#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <tuple>
#include <cmath>
#include <numeric>
#include <functional>
#include <cassert>
#include <atcoder/modint>

#define debug_value(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << #x << "=" << x << endl;
#define debug(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << x << endl;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

using namespace std;
typedef long long ll;

template<typename T>
vector<vector<T>> vec2d(int n, int m, T v){
    return vector<vector<T>>(n, vector<T>(m, v));
}

template<typename T>
vector<vector<vector<T>>> vec3d(int n, int m, int k, T v){
    return vector<vector<vector<T>>>(n, vector<vector<T>>(m, vector<T>(k, v)));
}

template<typename T>
void print_vector(vector<T> v, char delimiter=' '){
    if(v.empty()) {
        cout << endl;
        return;
    }
    for(int i = 0; i+1 < v.size(); i++) cout << v[i] << delimiter;
    cout << v.back() << endl;
}

using mint = atcoder::modint998244353;

ostream& operator<<(ostream& os, const mint& m){
    os << m.val();
    return os;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    int h, w, n, k; cin >> h >> w >> n >> k;
    auto make_v = [&](int len){
        vector<int> ans(k+1);
        if(len >= 2*k+1){
            for(int x = 1; x < k; x++) ans[x] = 2;
            ans[k] = len-2*(k-1);
            return ans;
        }
        int rem = len;
        for(int i = 0; i < len; i++){
            int l = max(0, i-k+1);
            int r = min(i, h-k);
            ans[r-l+1]++;
        }
        return ans;
    };
    vector<int> cx = make_v(h);
    vector<int> cy = make_v(w);
    // print_vector(cx);
    mint ans = 0;
    mint area = mint(h-k+1)*mint(w-k+1);
    for(int x = 1; x <= k; x++){
        for(int y = 1; y <= k; y++){
            mint ok_area = mint(x)*mint(y);
            mint rem_area = area-ok_area;
            mint p_ng = rem_area/area;
            mint p_all_ng = p_ng.pow(n);
            ans += (1-p_all_ng)*cx[x]*cy[y];
        }
    }
    cout << ans << endl;
}