#include<queue>
#include<math.h>
#include<stdio.h>
#include<string.h>
#include<iostream>
#include<algorithm>
using namespace std;

#define LL long long
#define N 123456789
#define M 1234
const double PI = acos(-1.0);
const double ee = 1e-8;

double r,R,H,V,v;

double calc(double h)
{
    double x=r+h/H*(R-r);
    return PI*h*(r*r+x*x+r*x)/3;
}

int main()
{
    int t;cin>>t;
    while(t--)
    {
        scanf("%lf%lf%lf%lf",&r,&R,&H,&V);
        double ll=0,rr=H,mid;
        while(ll<=rr)
        {
            mid=(ll+rr)/2;
            v=calc(mid);
            if(fabs(v-V)<=ee)
                break;
            else if(v<V)
                ll=mid+ee;
            else
               rr=mid-ee;
        }
        printf("%.6f\n",mid);
    }
    return 0;
}