#include <bits/stdc++.h>
using namespace std;
long long n, m, k, ms, pts, secs[200005], secp[200005], pots[200005],
    potsp[200005];
int main() {
  cin >> n >> m >> k;
  cin >> ms >> pts;
  for (long long i = 0; i < m; i++) cin >> secs[i];
  for (long long i = 0; i < m; i++) cin >> secp[i];
  for (long long i = 0; i < k; i++) cin >> pots[i];
  for (long long i = 0; i < k; i++) cin >> potsp[i];
  long long ans = ms * n;
  for (long long i = 0; i < m; i++) {
    long long lo = 0, hi = k - 1;
    while (lo <= hi) {
      long long mid = (lo + hi) / 2;
      long long temp_pts = secp[i] + potsp[mid];
      if (temp_pts <= pts) {
        long long temp_ans = secs[i] * (n - pots[mid]);
        if (temp_ans < ans) {
          ans = temp_ans;
          lo = mid + 1;
        } else {
          lo = mid + 1;
        }
      } else {
        hi = mid - 1;
      }
    }
  }
  for (long long i = 0; i < m; i++)
    if (((secs[i] * n) < ans) && (secp[i] <= pts)) ans = secs[i] * n;
  for (long long i = 0; i < k; i++) {
    if (potsp[i] > pts) break;
    if (ms * (n - pots[i]) < ans) ans = ms * (n - pots[i]);
  }
  cout << ans << endl;
  return 0;
}
