import decimal
t = int(input())
for i in range(t):
    ans = 0
    p,k = input().split()
    p = float(p)
    k = int(k)

    q = 1 - p
    for j in range(1,k):
        ans += pow(q,j-1)*p*j
    ans += pow(q,k-1)*k
    print(ans)