from collections import defaultdict


MOD = 998244353 

def f(x, K):
    ans = defaultdict(int)
    if x <= 2 * K:
        for i in range(x):
            ans[(min(i + K - 1, x - 1) - max(i - K + 1, 0) + 2 - K) % MOD] += 1
    else:
        for i in range(K):
            ans[(min(i + K - 1, x - 1) - max(i - K + 1, 0) + 2 - K) % MOD] += 1
        for i in range(x - 1, x - 1 - K, -1):
            ans[(min(i + K - 1, x - 1) - max(i - K + 1, 0) + 2 - K) % MOD] += 1
        ans[K] += x - 2 * K
    return ans

H, W, N, K = map(int, input().split())

s0 = f(H, K)
s1 = f(W, K)

C = pow(((H - K + 1) * (W - K + 1)) % MOD, MOD - 2, MOD)

ans = 0
for i in s0:
    for j in s1:
        res = (1 - pow((1 - C * i * j) % MOD, N, MOD)) % MOD
        ans += res * s0[i] * s1[j]
        ans %= MOD
print(ans)