T = int(input())
for _ in range(T):
    ss = input().split()
    p, K = float(ss[0]), int(ss[1])

    # 期待値 = \sum 確率 * 値
    q = 1 - p
    ans = 0
    for i in range(1, K):
        ans += p * pow(q, i-1) * i
    ans += pow(q, K-1) * K
    print(ans)