#!/usr/bin/env python3

'''Problem B: Cookie Clicker Alpha https://code.google.com/codejam/contest/2974486/dashboard#s=p1'''

def solve(c, f, x):
    rate, total = 2.0, 0
    m = x / rate
    while m <= x:
        total += (c / rate)
        rate += f
        t = total + (x / rate)
        if m < t:
            break
        else:
            m = t
    return m

for x in range(int(input())):
    nums = input().split()
    ans = solve(float(nums[0]), float(nums[1]), float(nums[2]))
    print('Case #{}: {:.8f}'.format(x + 1, ans))