mod = 998244353
inv2 = mod + 1 >> 1

t = int(input())
for i in range(t):
	n, m = map(int, input().split())
	if n == 1:
		print(0)
		continue
	p = n * (n - 1) // 2
	c = pow(m, n, mod) * ((m - 1) * inv2) % mod
	print(c * p % mod)