for _ in range(int(input())):
    li = list(map(str,input().split()))
    p = float(li[0])
    K = int(li[1])
    ans = 0
    for i in range(1,K):
        ans += i * p * ((1-p)**(i-1))
    ans += K * ((1-p)**(K-1))
    print(ans)