T=int(input())
mod = 998244353
ans = []
for _ in range(T):
    N, M = map(int,input().split())
    ans_d = N*(N-1)//2
    ans_d *= pow(M, N - 2, mod)
    # (3*(3-1)//2)**2
    ans_d *= (M*(M-1)*M - M*((M*(M-1)//2)))
    ans_d %= mod
    ans.append(ans_d)
for a in ans:
    print(a)