MOD = 998244353
from math import comb
# from itertools import product
# def naive(n,m):
#     ret = 0
#     for A in product(range(m),repeat=n):
#         for i in range(n):
#             for j in range(i+1,n):
#                 ret += (A[i] + A[j]) % m
#     return ret

# for N in range(1,11):
#     for M in range(1,11):
#         print(naive(N,M),end=" ")
#     print()

# 0 0 0 0 0 0 0 0 0 0 
# 0 2 9 24 50 90 147 224 324 450 
# 0 12 81 288 750 1620 3087 5376 8748 13500 
# 0 48 486 2304 7500 19440 43218 86016 157464 270000 
# 0 160 2430 15360 62500 194400 504210 1146880 2361960 4500000 
# 0 480 10935 92160 468750 1749600 5294205 13762560 31886460 67500000 
# 0 1344 45927 516096 3281250 14696640 51883209 154140672 401769396 945000000 
# 0 3584 183708 2752512 21875000 117573120 484243284 1644167168 4821232752

# 縦で見ると
# A001788: https://oeis.org/A001788 * 2
# A027472: https://oeis.org/A027472 * 9
# A038845: https://oeis.org/A038845 * 24

# 横で見ると
#A006002: https://oeis.org/A006002

def A006002(n):return n * (n+1) * (n+1) // 2

# for N in range(1,11):
#     for M in range(1,11):
#         print(A006002(M-1) * M**(N-1) * comb(N+1,2),end=" ")
#     print()
# print([A006002(1) * 2**(N-1) * comb(N+1,2) for N in range(1,11)])
# print([A006002(2) * 3**(N-1) * comb(N+1,2) for N in range(1,11)])
# print([A006002(3) * 4**(N-1) * comb(N+1,2) for N in range(1,11)])

T = int(input())
for _ in range(T):
    N,M = list(map(int,input().split()))
    print(A006002(M-1) * pow(M,N-2,MOD) * comb(N,2) % MOD)