#include <bits/stdc++.h>
using namespace std;

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

    int T;
    cin >> T;

    cout << fixed << setprecision(3);

    while (T--) {
        double V, Tm, T0, L;
        cin >> V >> Tm >> T0 >> L;

        double time = 0;

        while (true) {
            double dist = V * Tm;

            if (L <= dist) {
                time += L / V;
                break;
            } else {
                L -= dist;
                time += Tm;
                if (L <= 1e-12) break;
                time += T0;
            }
        }

        cout << time << "\n";
    }

    return 0;
}

C++ :

#include <stdio.h>

int main()
{
  int casc;
  scanf("%d", &casc);
  for (int casi = 1; casi <= casc; casi++) {
    int v, t, t0, l;
    scanf("%d %d %d %d", &v, &t, &t0, &l);
    int s = v * t;
    double res = l / s * (t + t0);
    if (l % s == 0)
      res -= t0;
    else res += 1.0 * (l % s) / v;
    printf("%.3f\n", res);
  }
  return 0;
}