C :

#include <stdio.h>
int main(){
    int m,n,x,y,z,t;
    double r;
    scanf("%d",&n);
    while(n--){
        scanf("%d%d%d%d",&m,&x,&y,&z);
        r=(double)m*x/(y-x)*z;
        printf("%.2f\n",r);
    }
    return 0;
}

Java :

import java.util.Scanner;
public class Main
{
	public static void main(String[] args)
	{
		Scanner sc=new Scanner(System.in);
		int N=sc.nextInt();
		while(N-->0)
		{
			int M=sc.nextInt();
			int X=sc.nextInt();
			int Y=sc.nextInt();
			int Z=sc.nextInt();
			getRange(M,X,Y,Z);
		}
	}
	public static void getRange(int a,int b,int c,int d)
	{
		float minutes=(float)(a*b/(float)(c-b));
		System.out.printf("%.2f\n",(d*minutes));
	}
}