1. 

/**
* ACM Training
* Problem 10773-Back to Intermediate Math
* Zeit: 0.176
* Status: ACCEPTED
* @author Christoph Miesel
*/

import java.util.*;

public class Fluss
{
public static double calc(double d, double v, double u)
{
if(u==0 || v==0 || u<=v)
return 0;
return Math.abs(d/u - d/Math.sqrt(u*u-v*v));
}

public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
int cases = sc.nextInt();
double v, u, d;

for(int c = 1; c <= cases; c++)
{
d = sc.nextDouble();
v = sc.nextDouble();
u = sc.nextDouble();
double tmp = calc(d,v,u);
if(tmp != 0)
System.out.printf("Case %d: %.3f%n", c, tmp);
else System.out.printf("Case %d: can't determine%n",c);
}
}
}