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