import sys, time, random
from collections import deque, Counter, defaultdict
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
inf = 2 ** 63 - 1
mod = 998244353

for _ in range(ii()):
    p, k = input().split()
    p = float(p)
    k = int(k)
    q = 1
    ans = 0
    for i in range(1, k):
        ans += i * p * q
        q *= (1 - p)
    ans += q * k
    print(ans)