C :

#include<stdio.h>
int main()
{
int  a,i,j;
	double d=0.0,b,c;
	scanf("%d",&a);
	for(i=0;i<a;i++)
	{
		scanf("%lf%lf",&b,&c);
			d=b;
		for(j=2;j<=c;j++)
		{
			b=b/2.0;
		d=b*2.0+d;
		
		}
		printf("%.2f\n",d);
		
	}
	return 0;
}

		

C++ :

#include <cstdio>
#include <cmath>

double fun(int n) {
    if (1 == n)
        return 1;
    else
        return fun(n - 1) + 1.0 / pow(2.0, n - 2);
}

int main() {
    //freopen("test.in", "r", stdin);
    //freopen("test.out", "w", stdout);
    int t;
    scanf("%d", &t);
    while (t--) {
        int h, n;
        scanf("%d %d", &h, &n);
        printf("%.2f\n", fun(n) * h);
    }
    return 0;
}