#include <bits/stdc++.h>
using namespace std;
vector<long long> a, b, c, d;
int main() {
  ios_base::sync_with_stdio(false);
  long long n, i, j, temp, x, k, m, s;
  long long ans;
  cin >> n >> m >> k;
  cin >> x >> s;
  for (i = 0; i < m; i++) {
    cin >> temp;
    a.push_back(temp);
  }
  for (i = 0; i < m; i++) {
    cin >> temp;
    b.push_back(temp);
  }
  for (i = 0; i < k; i++) {
    cin >> temp;
    c.push_back(temp);
  }
  for (i = 0; i < k; i++) {
    cin >> temp;
    d.push_back(temp);
  }
  ans = n * x;
  for (i = 0; i < m; i++) {
    temp = 1e19;
    auto it = upper_bound(d.begin(), d.end(), s - b[i]);
    int ind = it - d.begin();
    if (it != d.begin()) temp = (n - c[ind - 1]) * a[i];
    if (b[i] <= s) temp = min(temp, n * a[i]);
    if (ans > temp) ans = temp;
  }
  auto it = upper_bound(d.begin(), d.end(), s);
  int ind = it - d.begin();
  if (it != d.begin()) ans = min(ans, (n - c[ind - 1]) * x);
  cout << ans;
  return 0;
}
