#include <bits/stdc++.h>
using namespace std;
long long int SearchPos(long long int d[], long long int lb, long long int ub,
                        long long int key) {
  long long int mid;
  while (lb <= ub) {
    mid = (lb + ub) / 2;
    if (d[mid] <= key && (mid == ub || d[mid + 1] > key))
      return mid;
    else if (d[mid] > key)
      ub = mid - 1;
    else
      lb = mid + 1;
  }
  return -1;
}
int main() {
  long long int n, m, k, i, j, x, y, z, ans = 0, s;
  cin >> n >> m >> k;
  long long int a[m], b[m], c[k], d[k];
  cin >> x >> s;
  for (i = 0; i < m; i++) cin >> a[i];
  for (i = 0; i < m; i++) cin >> b[i];
  for (i = 0; i < k; i++) cin >> c[i];
  for (i = 0; i < k; i++) cin >> d[i];
  ans = x * n;
  for (i = k - 1; i >= 0; i--) {
    if (d[i] <= s) {
      ans = min(ans, x * (n - c[i]));
      break;
    }
  }
  for (i = 0; i < m; i++) {
    if (b[i] <= s) {
      z = SearchPos(d, 0, k - 1, s - b[i]);
      if (z == -1)
        ans = min(ans, a[i] * n);
      else
        ans = min(ans, a[i] * (n - c[z]));
    }
  }
  cout << ans << endl;
  return 0;
}
