T = int(input())
for i in range(T):
    p, K = input().split()
    K = int(K)
    p = float(p)
    ans = 0
    q = 1 - p
    for j in range(1, K):
        ans += j * q**(j - 1) * p
    # K回目
    ans += q**(K - 1) * K
    print(ans)