#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n, m, k, x, s, i, minn1, cost, *t;
  cin >> n >> m >> k >> x >> s;
  long long a[m], b[m], c[k], d[k], minn = n * x;
  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];
  }
  t = upper_bound(d, d + k, s);
  if (t - &d[0] != 0) {
    cost = x * (n - (c[t - &d[0] - 1]));
  }
  if (cost < minn) minn = cost;
  for (i = 0; i < m; i++) {
    long long t1;
    t1 = s - b[i];
    if (t1 >= 0) {
      t = upper_bound(d, d + k, t1);
      if (t - &d[0] == 0) {
        cost = a[i] * (n);
        if (cost < minn) minn = cost;
      } else {
        cost = a[i] * (n - (c[t - &d[0] - 1]));
        if (cost < minn) minn = cost;
      }
    }
  }
  cout << minn;
  return 0;
}
