1 #include<stdio.h>
 2 int main()
 3 {
 4     int n;
 5     double m,x,y,z;
 6     scanf("%d",&n);
 7     while(n--)
 8     {
 9         scanf("%lf%lf%lf%lf",&m,&x,&y,&z);
10         printf("%.2lf\n",(m*x)/(y-x)*z);
11     }
12 }