#include<iostream>
#include<cmath>
using namespace std;
int main()
{
int n;
cin>>n;
double a,b,c,d,res,h;
for(int i=0;i<n;i++)
{
cin>>a>>b>>c>>d;
h=((d*d)-(b*b)+abs((a-c)*(a-c)))/abs((2*a)-(2*c));
h=sqrt((d*d)-(h*h));
res=(a+c)*h;
res=0.5*res;
cout<<"Case "<<i+1<<": "<<res<<endl;
}
return 0;
}
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