#include <stdio.h>
#include <conio.h>
#include <math.h>

float const pi=4.0*atan(1.0);
main(){
       float rf,r1,r2,v1,v2,out;
       rf = 10000.0;
       r1 = 4700.0;
       r2 = 1000.0;
       v1 = 5.0;
       v2 = 10.0;
       out = ((-rf/r1)*v1)*((-rf/r2)*v2);
       printf("answer is %.4f", out);
       while(!kbhit()){}
}