#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
using ll = long long;
mint mpow(mint a, ll n) {
	mint ret = 1;
	while (n) {
		if (n & 1) ret *= a;
		n >>= 1;
		a = a * a;
	}
	return ret;
}
int main () {
	ll H, W;
	ll N, K;
	cin >> H >> W >> N >> K;
	if (H > W) swap(H, W);
	mint h = H, w = W;
	if (H < 2 * K - 1) {
		if (W < 2 * K - 1) {
			mint ans = 0;
			for (ll i = 0; i < H; i ++) {
				for (ll j = 0; j < W; j ++) {
					ll dh = (min(i, H - K) - max(0ll, i - K + 1)) + 1;
					ll dw = (min(j, W - K) - max(0ll, j - K + 1)) + 1;
					mint p = dh * dw;
					p /= h * w;
					ans += 1 - mpow(1 - p, N);
				}
			}
			cout << ans.val() << endl;
		} else {
			mint ans = 0;
			for (ll i = 0; i < H; i ++) {
				ll dh = min(i, H - K) - max(0ll, i - K + 1) + 1;
				for (ll j = 0; j < K - 1; j ++) {
					ll dw = min(j, W - K) - max(0ll, j - K + 1) + 1;
					mint p = dh * dw;
					p /= h * w;
					ans += 1 - mpow(1 - p, N);
				}
				ll wn = W - 2 * (K - 1);
				mint p_ = dh * (ll)(K);
				p_ /= h * w;
				ans += 1 - mpow(1 - p_, N);
				for (ll j = W - K + 1; j < W; j ++) {
					ll dw = min(j, W - K) - max(0ll, j - K + 1) + 1;
					mint p = dh * dw;
					p /= h * w;
					ans += 1 - mpow(1 - p, N);
				}
			}
			cout << ans.val() << endl;
		}
	} else {
		mint ans = 0;
		for (ll i = 0; i < K - 1; i ++) {
			for (ll j = 0; j < K - 1; j ++) {
				ll dh = i + 1, dw = j + 1;
				mint p = dh * dw;
				p /= h * w;
				mint p2 = 1 - mpow(1 - p, N);
				ans += 4 * p2;
			}
		}
		for (ll i = 0; i < K - 1; i ++) {
			ll dh = i + 1, dw = K;
			mint p = dh * dw;
			p /= h * w;
			mint p2 = 1 - mpow(1 - p, N);
			ans += p2 * 2 * (W - 2 * (K - 1));
		}
		for (ll j = 0; j < K - 1; j ++) {
			ll dh = K, dw = j + 1;
			mint p = dh * dw;
			p /= h * w;
			mint p2 = 1 - mpow(1 - p, N);
			ans += p2 * 2 * (H - 2 * (K - 1));
		}
		mint p = K * K;
		p /= h * w;
		mint p2 = 1 - mpow(1 - p, N);
		ans += p2 * (H - 2 * (K - 1)) * (W - 2 * (K - 1));
		cout << ans.val() << endl;
	}
}