#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  long long n, m, k;
  cin >> n >> m >> k;
  long long x, s;
  cin >> x >> s;
  vector<int> a;
  vector<int> b;
  vector<int> c;
  vector<int> d;
  for (long long i = 0; i < m; i++) {
    long long now;
    cin >> now;
    a.push_back(now);
  }
  for (long long i = 0; i < m; i++) {
    long long now;
    cin >> now;
    b.push_back(now);
  }
  for (long long i = 0; i < k; i++) {
    long long now;
    cin >> now;
    c.push_back(now);
  }
  for (long long i = 0; i < k; i++) {
    long long now;
    cin >> now;
    d.push_back(now);
  }
  long long answer = n * x;
  long long v = x;
  long long L = -1;
  long long R = k;
  while (R - L > 1) {
    long long mid = L + (R - L) / 2;
    if (d[mid] <= s) {
      L = mid;
    } else {
      R = mid;
    }
  }
  long long kol = n;
  if (L > -1) {
    kol = n - c[L];
  }
  long long ans = kol * v;
  if (ans < answer) {
    answer = ans;
  }
  for (long long i = 0; i < m; i++) {
    long long now = s - b[i];
    if (now >= 0) {
      v = a[i];
      L = -1;
      R = k;
      while (R - L > 1) {
        long long mid = L + (R - L) / 2;
        if (d[mid] <= now) {
          L = mid;
        } else {
          R = mid;
        }
      }
      kol = n;
      if (L > -1) {
        kol = n - c[L];
      }
      ans = kol * v;
      if (ans < answer) {
        answer = ans;
      }
    }
  }
  cout << answer;
  return 0;
}
