import sys
input = sys.stdin.readline

T=int(input())
for tests in range(T):
    p,K=map(float,input().split())
    K=int(K)

    ANS=0
    now=1

    for i in range(K):
        if i!=K-1:
            ANS+=(i+1)*now*p
        else:
            ANS+=(i+1)*now
        now=now*(1-p)

    print(ANS)