import sys
input = sys.stdin.readline

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