#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n, m, k, x, s;
  cin >> n >> m >> k;
  cin >> x >> s;
  long long int Array1[m + 1];
  long long int Array11[m + 1];
  for (int i = 1; i <= m; i++) cin >> Array1[i];
  for (int i = 1; i <= m; i++) cin >> Array11[i];
  long long int Array2[k + 1];
  long long int Array22[k + 1];
  for (int i = 1; i <= k; i++) cin >> Array2[i];
  for (int i = 1; i <= k; i++) cin >> Array22[i];
  Array1[0] = x;
  Array11[0] = 0;
  Array2[0] = 0;
  Array22[0] = 0;
  long long int ans = n * Array1[0];
  for (int i = 0; i <= m; i++) {
    int l = 0, r = k;
    while (l <= r) {
      int mid = (l + r) / 2;
      if (Array11[i] + Array22[mid] <= s) {
        ans = min(ans, (n - Array2[mid]) * Array1[i]);
        l = mid + 1;
        if (ans == 0) {
          cout << 0 << "\n";
          return 0;
        }
      } else
        r = mid - 1;
    }
  }
  cout << ans << "\n";
}
