独立考虑，最后推出公式。0.5-0.5*pow(1-p-p,1.0*k);

#include <iostream>

#include <functional>

#include <algorithm>

#include <complex>

#include <cstdlib>

#include <cstring>

#include <fstream>

#include <iomanip>

#include <sstream>

#include <utility>

#include <bitset>

#include <cctype>

#include <cstdio>

#include <limits>

#include <memory>

#include <string>

#include <vector>

#include <cmath>

#include <ctime>

#include <queue>

#include <stack>

#include <list>

#include <map>

#include <set>

using namespace std;

typedef long long LL;

double dp[2][5010][2];

int m1, m2;

double get(double i,double x)

{

    return 1.0-((i-1.0)*(i-1.0)+(x-i)*(x-i))/x/x;

}

int main()

{

    int t, icase = 1;

    scanf("%d", &t);

    while (t--)

    {

        int x,y,z,k;

        scanf ("%d%d%d%d",&x,&y,&z,&k);

        double ans=0;

        for (int i=1;i<=x;i++)

        {

            for (int j=1;j<=y;j++)

            {

                for (int l=1;l<=z;l++)

                {

                    double p=get(i,x)*get(j,y)*get(l,z);

                    ans+=0.5-0.5*pow(1-p-p,1.0*k);

                }

            }

        }

        printf("Case %d: %.12f\n", icase++, ans);

    }

    return 0;

}