import java.util.*;
	public class Main{
		public static void main(String[]args){
			Scanner sc=new Scanner (System.in);
			int t=sc.nextInt();
			double x,s,h,ta,trapa;
			if(t<=20){
				for(int i=1;i<=t;i++){
				double a=sc.nextDouble();
				double b=sc.nextDouble();
				double c=sc.nextDouble();
				double d=sc.nextDouble();
				x=Math.abs(a-c);
				s=0.5*(x+b+d);
				ta=Math.sqrt((s*(s-x)*(s-b)*(s-d)));
				h=(ta*2)/x;
				trapa=0.5*(a+c)*h;
				if(trapa>=0 && trapa<=200){
					System.out.printf("%.4f%n Case"+i+": "+trapa);
				}
			}
		}
		}
	}

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Mgo2IDUgMTIgNS4wCjkgNSA2IDQ=

2
6 5 12 5.0
9 5 6 4