Untitled

#include <bits/stdc++.h>

#define all(x) x.begin(), x.end()
#define r_all(x) x.rbegin(), x.rend()
#define sz(x)(ll) x.size()
#define g_max(x, y) x = max(x, y)
#define g_min(x, y) x = min(x, y)
#define rsz(a, n) a.resize(n)
#define ass(a, n) a.assign(n, 0)
#define YES() cout << "YES\n"
#define Yes cout << "Yes\n"
#define NO() cout << "NO\n"
#define No() cout << "No\n"
#define endl "\n"
#define print(a) for (auto &x: a) cout << x << " "; cout << endl
#define print_pair(a)
#define FOR(i, fr, to) for (long long i = fr; i <= to; i++)
#define RFOR(i, fr, to) for (long long i = fr; i >= to; i--)
#define pb push_back
#define eb emplace_back
#define is insert
#define F first
#define S second

using namespace std;

using ll = long long;
using ld = long double;

using vll = vector<ll>;
using vvll = vector<vll>;
using vc = vector<char>;
using vvc = vector<vc>;
using pll = pair<ll, ll>;
using vpll = vector<pll>;
using vvpll = vector<vpll>;
using stkll = stack<ll>;
using qll = queue<ll>;
using dqll = deque<ll>;
using sll = set<ll>;
using msll = multiset<ll>;
using mll = map<ll, ll>;
using vsll = vector<sll>;
using sc = set<char>;
using pcll = pair<char, ll>;

ll dr[] = {0, 1, 0, -1}, dc[] = {-1, 0, 1, 0};

const ll INF = 1e18;
ll MOD = 998244353;

ll mod_add(ll u, ll v, ll mod = MOD) {
    u %= mod, v %= mod;
    return (u + v) % mod;
}

ll mod_sub(ll u, ll v, ll mod = MOD) {
    u %= mod, v %= mod;
    return (u - v + mod) % mod;
}

ll mod_mul(ll u, ll v, ll mod = MOD) {
    u %= mod, v %= mod;
    return (u * v) % mod;
}

ll mod_pow(ll u, ll p, ll mod = MOD) {
    u %= mod;
    if (p == 0) {
        return 1;
    }

    ll v = mod_pow(u, p / 2, mod) % mod;
    v = (v * v) % mod;
    return (p % 2 == 0) ? v : (u * v) % mod;
}

ll mod_inv(ll u, ll mod = MOD) {
    u %= mod;
    ll g = __gcd(u, mod);
    if (g != 1) {
        return -1;
    }

    return mod_pow(u, mod - 2, mod);
}

ll mod_div(ll u, ll v, ll mod = MOD) {
    u %= mod, v %= mod;
    return mod_mul(u, mod_inv(v), mod);
}


template<class T>
vector<T> operator+(vector<T> a, vector<T> b) {
    a.insert(a.end(), b.begin(), b.end());
    return a;
}

pll operator+(pll a, pll b) {
    pll ans = {a.first + b.first, a.second + b.second};
    return ans;
}

template<class A, class B>
ostream &operator<<(ostream &os,
                    const pair<A, B> &p) {
    os << p.first << " " << p.second;
    return os;
}

template<class A, class B>
istream &operator>>(istream &is, pair<A, B> &p) {
    is >> p.first >> p.second;
    return is;
}

template<class T>
ostream &operator<<(ostream &os,
                    const vector<T> &vec) {
    for (auto &x: vec) {
        os << x << " ";
    }

    return os;
}

template<class T>
istream &operator>>(istream &is, vector<T> &vec) {
    for (auto &x: vec) {
        is >> x;
    }

    return is;
}


template<class T>
ostream &operator<<(ostream &os,
                    const set<T> &vec) {
    for (auto &x: vec) {
        os << x << " ";
    }

    return os;
}

template<class A, class B>
ostream &operator<<(ostream &os,
                    const map<A, B> d) {
    for (auto &x: d) {
        os << "(" << x.first << " " << x.second << ") ";
    }

    return os;
}

template<class A>
void read_arr(A a[], ll from, ll to) {
    for (ll i = from; i <= to; i++) {
        cin >> a[i];
    }
}

template<class A>
void print_arr(A a[], ll from, ll to) {
    for (ll i = from; i <= to; i++) {
        cout << a[i] << " ";
    }
    cout << "\n";
}

template<class A>
void print_arr(A a[], ll n) {
    print_arr(a, 0, n - 1);
}

template<class A>
void set_arr(A a[], A val, ll from, ll to) {
    for (ll i = from; i <= to; i++) {
        a[i] = val;
    }
}

template<class A>
void set_arr(A a[], A val, ll n) {
    set_arr(a, val, 0, n - 1);
}


const ll N = 2e5 + 10;



ll n, k, q;
ll a[N];
string s, s1, s2, s3;

struct Dsu {
    ll par[N];
    ll n;

    void init(ll _n) {
        n = _n;
    }

    void build() {
        FOR(i, 0, n) {
            par[i] = -1;
        }
    }

    ll get(ll x) {
        return par[x] < 0 ? x : par[x] = get(par[x]);
    }

    ll same_set(ll a, ll b) {
        return get(a) == get(b);
    }

    ll size(ll x) {
        return -par[get(x)];
    }

    ll unite(ll x, ll y) {
        x = get(x), y = get(y);

        if (x == y) {
            return false;
        }

        if (par[x] > par[y]) {
            swap(x, y);
        }

        par[x] += par[y], par[y] = x;
        return 1;
    }


};

struct E {
    ll u, v, w;

    bool operator<(const E &o) const {
        return w < o.w;
    }
};

void init() {
}

struct B {
    double a, b, t;
};

struct comp {
    bool operator()(const B &o1, const B &o2) const {
        return o1.t + o1.a / o1.b > o2.t + o2.a / o2.b;
    }
};

vector<B> vec;
double m;

ll valid(double x) {
    priority_queue<B, vector<B>, comp> pq;
    for (auto &p: vec) {
        B tmp{p.a, p.b, p.t};
        pq.push(tmp);
    }

    double cur = 0;
    while (cur < x) {
        B u = pq.top();
        pq.pop();

        B nxt = pq.top();
        double nxt_t = min(x, nxt.a / nxt.b + nxt.t);
        u.a = (m - u.b) * (nxt_t - cur) + u.a;
        u.t = cur;

        cout << make_pair(u.a, u.b) << " " << u.t << "\n";


        if (abs(u.a) <= 1e-7) {
            return false;
        }


        cur = nxt_t;
        pq.push(u);

    }

    return true;
}

double get_ans() {
    double left = 0, right = 0;
    double eps = 1e-5;

    for (auto &u: vec) {
        g_max(right, u.a / u.b);
    }

    if (n == 1) {
        return (m >= vec[0].b) ? -1 : vec[0].a / (vec[0].b - m);
    }

//    while (left + eps < right) {
//        double mid = (left + right) / 2;
////        cout << make_pair(left, right) << '\n';
//        if (valid(mid)) {
//            left = mid + eps;
//        } else {
//            right = mid;
//        }
//    }

    cout << valid(0.6) << "\n";

    return left - eps;
}

void single(ll t_id = 0) {
    cin >> n >> m;

    vec.clear();
    FOR(i, 1, n) {
        B u {};
        cin >> u.b >> u.a;
        vec.push_back(u);
    }

    cout << get_ans() << "\n";
}

void multiple() {

    ll t;
    cin >> t;

    for (ll i = 0; i < t; i++) {
        single(i);
    }



}

//#endif

#if 0

void multiple() {
    while (cin >> n >> m) {
        if (n == 0 && m == 0) {
            break;
        }

        single();
    }

#endif

int main(int argc, char *argv[]) {
//    ios_base::sync_with_stdio(false);
//    cin.tie(nullptr);

    init();


//    freopen("feast.in", "r", stdin);
//    freopen("feast.out", "w", stdout);

    freopen("../input.txt", "r", stdin);
    multiple();
//    single();




    return 0;


};