include

using namespace std;

int main() {

int n;
cin >> n;
int a, b, c, d;
for (int i = 1; i <= n; i++) {
	cin >> a >> b >> c >> d;
	double n1, n2;
	n1 = double(a) / b;
	n2 = double(c) / d;
	double f = n1 * n2;
	printf("%.6lf\n", f);
}
return 0;

}