#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <atcoder/modint>
using namespace std;
using i32 = int;
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;
#define rep(i,n) for(int i=0; i<(int)(n); i++)
const i64 INF = 1001001001001001001;

using Modint = atcoder::static_modint<998244353>;

int main(){
    i64 H, W, N, K; cin >> H >> W >> N >> K;
    i64 f = (H-K+1) * (W-K+1);
    Modint p = (Modint(f)).inv().pow(N);
    Modint ans = 0;
    for(i64 x=1; x<K && x*2-1<=W; x++) for(i64 y=1; y<K && y*2-1<=H; y++){
        Modint tmp = Modint(f-min(x,W-K+1)*min(y,H-K+1)).pow(N);
        int dcnt = 1;
        if(x*2 <= W) tmp += tmp;
        if(y*2 <= H) tmp += tmp;
        ans += tmp;
    }
    if(W >= 2*K-2){
        for(i64 y=1; y<K && y*2-1<=H; y++){
            Modint tmp = Modint(f-K*min(y,H-K+1)).pow(N) * (W-(2*K-2));
            if(y*2 <= H) ans += tmp;
            ans += tmp;
        }
    }
    if(H >= 2*K-2){
        for(i64 x=1; x<K && x*2-1<=W; x++){
            Modint tmp = Modint(f-K*min(x,W-K+1)).pow(N) * (H-(2*K-2));
            if(x*2 <= W) ans += tmp;
            ans += tmp;
        }
    }
    if(W >= 2*K-2 && H >= 2*K-2){
        ans += Modint(f-K*K).pow(N) * (H-(2*K-2)) * (W-(2*K-2));
    }
    ans *= p;
    ans = Modint(H*W) - ans;
    cout << ans.val() << endl;
    return 0;
}


struct ios_do_not_sync{
    ios_do_not_sync(){
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
    }
} ios_do_not_sync_instance;