Untitled

#include <bits/stdc++.h>

#define ll long long
#define stp(n) fixed<<setprecision(n)
#define flash cin.tie(0); cin.sync_with_stdio(0);
#define el '\n'
# define pll pair<ll,ll>
# define pi pair<int,int>
#define popCnt(x) (__builtin_popcountll(x))
#define LSB(x) (__builtin_ffsll(x) - 1)
#define MSB(x) (64 - __builtin_clzll(x) - 1).

using namespace std;

//#pragma GCC optimize("03")
//#pragma GCC target("tune=native")
//#pragma GCC optimize("unroll-loops")

const ll mod = 1e9 + 7;

ll mul(const ll &a, const ll &b) {
    return (a % mod + mod) * (b % mod + mod) % mod;
}

ll add(const ll &a, const ll &b) {
    return (a + b + 2 * mod) % mod;
}

const int N = 5e3 + 9, inf = 2e9;
const ll infl = 2e18;

typedef vector<vector<double>> Matrix;


Matrix operator*(Matrix matrix1, Matrix matrix2) {
    int m1 = matrix1.size();
    int n1 = matrix1[0].size();
    int n2 = matrix2[0].size();
    Matrix result(m1, vector<double>(n2, 0));

    for (int i = 0; i < m1; ++i) {
        for (int j = 0; j < n2; ++j) {
            for (int k = 0; k < n1; ++k) {
                result[i][j] += matrix1[i][k] * matrix2[k][j];
//                result[i][j] %= mod;
            }
        }
    }

    return result;
}

Matrix binPow(Matrix a, long long b) {
    int n = a.size();
    Matrix res(n, vector<double>(n, 0));
    for (int i = 0; i < n; ++i) {
        res[i][i] = 1;
    }
    while (b > 0) {
        if (b & 1)
            res = res * a;
        a = a * a;
        b >>= 1;
    }
    return res;
}

const double den = (1.0 + ::sqrt(2.0));

void testCase() {
    int n;
    double r;
    cin >> r >> n;
    n = min(n, 50);
    double c1 = r * den, r1 = r;
    Matrix init = {{c1, r1},
                   {0,  0}};
    Matrix transition = {{1.0, 1.0 / den},
                         {-2,  -2.0 / den}};
    Matrix overallMalt = init * binPow(transition, n);
    cout << stp(7) << overallMalt[0][1] << el;

}


int main() {
    //    freopen("in.txt", "r", stdin);
//    freopen("out.txt", "w", stdout);

    flash;
    int T = 1;
    cin >> T;
    while (T--) {
        testCase();
//        cout << el;
//        cout << endl;
    }

}