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  #include <bits/stdc++.h>
  using namespace std;
  using ld = long double;

  int main() {
        ios::sync_with_stdio(false);
            cin.tie(nullptr);

                int c;
                    cin >> c;
                        cout.setf(ios::fixed);
                            cout << setprecision(15);

                                const ld PI = acosl(-1.0L);

                                    while (c--) {
                                                ld m, t;
                                                        cin >> m >> t;

                                                                if (t < 3 * m) {
                                                                                cout << 0.0 << "\n";
                                                                                            continue;
                                                                }

                                                                        ld best = 0.0;
                                                                                ld limit = min((ld)1e6L, floor(t / m));  // reasonable bound

                                                                                        for (ld n = 3; n <= limit; ++n) {
                                                                                                        ld walk = t - n * m;
                                                                                                                    if (walk <= 0) break;
                                                                                                                                ld area = (walk * walk) / (4.0L * n * tanl(PI / n));
                                                                                                                                            if (area > best) best = area;
                                                                                        }

                                                                                                // for huge n, approximate by circle
                                                                                                        if (t > 1e6 * m) {
                                                                                                                        ld walk = t - m * floor(t / m);
                                                                                                                                    ld circ = (walk * walk) / (4.0L * PI);
                                                                                                                                                best = max(best, circ);
                                                                                                        }

                                                                                                                cout << best << "\n";
                                    }
                                        return 0;
  }
                                                                                                        }
                                                                                        }
                                                                }
                                    }
  }