#############################################################

import sys
sys.setrecursionlimit(10**7)

from heapq import heappop,heappush
from collections import deque,defaultdict,Counter
from bisect import bisect_left, bisect_right
from itertools import product,combinations,permutations

ipt = sys.stdin.readline

def iin():
    return int(ipt())
def lmin():
    return list(map(int,ipt().split()))

MOD = 998244353
#############################################################

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