def main():
    t = int(input())
    for _ in range(t):
        p, k = input().split()
        p, k = float(p), int(k)
        e = 0
        z = 1
        for i in range(1, k):
            e += p * z * i
            z *= 1-p
        e += z * k
        print(e)


if __name__ == '__main__':
    main()