#include <bits/stdc++.h>
#include <atcoder/modint>
using namespace std;
using ll = long long;
using mint = atcoder::modint998244353;

int main() {
	ll h, w, n, k;
	cin >> h >> w >> n >> k;
	vector<mint> r(k + 1), c(k + 1);
	if (k * 2 <= h) {
		for (int i = 1; i <= k; i++) r[i] += 2;
		r[k] += h - k * 2;
	} else {
		for (int i = 1; i <= h - k; i++) r[i] += 2;
		r[h - k + 1] += 2 * k - h;
	}
	if (k * 2 <= w) {
		for (int i = 1; i <= k; i++) c[i] += 2;
		c[k] += w - k * 2;
	} else {
		for (int i = 1; i <= w - k; i++) c[i] += 2;
		c[w - k + 1] += 2 * k - w;
	}
	mint ans = 0, m = (h - k + 1) * (w - k + 1);
	for (int i = 1; i <= k; i++) {
		for (int j = 1; j <= k; j++) ans += r[i] * c[j] * (1 - ((m - i * j) / m).pow(n));
	}
	cout << ans.val() << endl;
}