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