#include <bits/stdc++.h>
#include <atcoder/convolution>
using namespace std;
const long long MOD = 998244353;
long long modpow(long long a, long long b){
  long long ans = 1;
  while (b > 0){
    if (b % 2 == 1){
      ans *= a;
      ans %= MOD;
    }
    a *= a;
    a %= MOD;
    b /= 2;
  }
  return ans;
}
long long modinv(long long a){
  return modpow(a, MOD - 2);
}
vector<long long> inverse(vector<long long> f){
  int N = f.size();
  vector<long long> ans(1);
  ans[0] = 1;
  for (int i = 1; i < N * 2; i *= 2){
    vector<long long> ans2 = ans;
    ans2.resize(i * 4);
    int N2 = min(N, i * 2);
    vector<long long> f2(i * 4, 0);
    for (int j = 0; j < N2; j++){
      f2[j] = f[j];
    }
    ans2 = atcoder::convolution(ans2, ans2);
    ans2.resize(i * 2);
    ans2 = atcoder::convolution(ans2, f2);
    ans2.resize(i * 2);
    for (int j = 0; j < i; j++){
      ans2[j] = MOD - ans2[j] + ans[j] * 2;
      ans2[j] %= MOD;
    }
    swap(ans, ans2);
  }
  ans.resize(N);
  return ans;
}
int main(){
  int H, W, N, K;
  cin >> H >> W >> N >> K;
  vector<long long> inv(N + 2);
  inv[1] = 1;
  for (int i = 2; i <= N + 1; i++){
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
  }
  vector<long long> fact(N + 2);
  vector<long long> finv(N + 2);
  fact[0] = 1;
  finv[0] = 1;
  for (int i = 1; i <= N + 1; i++){
    fact[i] = fact[i - 1] * i % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
  vector<long long> binom(N + 1);
  for (int i = 0; i <= N; i++){
    binom[i] = fact[N] * finv[i] % MOD * finv[N - i] % MOD;
  }
  int px = min(H - K + 1, K);
  int py = min(W - K + 1, K);
  int qx = H - 2 * (px - 1);
  int qy = W - 2 * (py - 1);
  long long C = MOD - modinv(H - K + 1) * modinv(W - K + 1) % MOD;
  vector<long long> POW_C(N + 1);
  vector<long long> POW_Cpx(N + 1);
  vector<long long> POW_Cpy(N + 1);
  POW_C[0] = 1;
  POW_Cpx[0] = 1;
  POW_Cpy[0] = 1;
  for (int i = 0; i < N; i++){
    POW_C[i + 1] = POW_C[i] * C % MOD;
    POW_Cpx[i + 1] = POW_Cpx[i] * C % MOD * px % MOD;
    POW_Cpy[i + 1] = POW_Cpy[i] * C % MOD * py % MOD;
  }
  auto solve = [&](long long N, int K){
    vector<long long> POW_N(K + 2);
    POW_N[0] = 1;
    for (int i = 0; i < K + 1; i++){
      POW_N[i + 1] = POW_N[i] * N % MOD;
    }
    vector<long long> num(K + 1, 0);
    for (int i = 0; i <= K; i++){
      num[i] = POW_N[i + 1] * finv[i + 1] % MOD;
    }
    vector<long long> den(K + 1, 0);
    for (int i = 0; i <= K; i++){
      den[i] = finv[i + 1];
    }
    vector<long long> den_inv = inverse(den);
    vector<long long> ans = atcoder::convolution(num, den_inv);
    for (int i = 0; i <= K; i++){
      ans[i] *= fact[i];
      ans[i] %= MOD;
    }
    ans[0]--;
    return ans;
  };
  vector<long long> sum_px = solve(px, N);
  vector<long long> sum_py = solve(py, N);
  long long ans1 = 0;
  for (int i = 0; i <= N; i++){
    ans1 += POW_C[i] * binom[i] % MOD * sum_px[i] % MOD * sum_py[i] % MOD;
  }
  ans1 %= MOD;
  ans1 *= 4;
  ans1 %= MOD;
  long long ans2 = 0;
  for (int i = 0; i <= N; i++){
    ans2 += POW_Cpy[i] * binom[i] % MOD * sum_px[i] % MOD;
  }
  ans2 %= MOD;
  ans2 *= 2 * qy;
  ans2 %= MOD;
  long long ans3 = 0;
  for (int i = 0; i <= N; i++){
    ans3 += POW_Cpx[i] * binom[i] % MOD * sum_py[i] % MOD;
  }
  ans3 %= MOD;
  ans3 *= 2 * qx;
  ans3 %= MOD;
  long long ans4 = modpow(MOD + 1 + C * px % MOD * py % MOD, N) * qx % MOD * qy % MOD;
  long long ans = (ans1 + ans2 + ans3 + ans4) % MOD;
  cout << ((long long) H * W % MOD - ans + MOD) % MOD << endl;
}