T = int(input())

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