#include<iostream>
#include<cstring>
#include<algorithm>
#include<iomanip>
using namespace std;

int X,Y,T,S;
int TT;

int main() {
    cin.sync_with_stdio(false);
    cin >> TT;
    int cas = 0;
    while (TT--) {
        cin >> X >> Y >> T >> S;
        cout<<"Case #"<<++cas<<": ";
        if (X <= Y || S <= Y * T) {
            cout << setprecision(3) << fixed << (double) S / X << endl;
            continue;
        }
        double L = Y * T;
        double now = 0;
        while (true) {
            double t = L / (X - Y);
            if (L + Y * t >= S) {
                now += (double) S / X;
                break;
            }
            now += t;
            L += Y * t;
        }
        cout << setprecision(3) << fixed << now << endl;
    }
    return 0;
}