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