#include <bits/stdc++.h>
using namespace std;
double dist(pair<int, int> a, pair<int, int> b) {
  return sqrt((a.first - b.first) * (a.first - b.first) +
              (a.second - b.second) * (a.second - b.second));
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long int a, b, c, n, m, p, q, k, total_cost;
  cin >> n >> m >> k;
  cin >> a >> b;
  total_cost = a * n;
  vector<long long int> f_time(m), f_cost(m), s_number(k), s_cost(k);
  for (auto &it : f_time) {
    cin >> it;
  }
  for (auto &it : f_cost) {
    cin >> it;
  }
  for (auto &it : s_number) {
    cin >> it;
  }
  for (auto &it : s_cost) {
    cin >> it;
  }
  long long int saved, cerch, total_saved = total_cost;
  for (int i = 0; i < m; i++) {
    cerch = b - f_cost[i];
    q = upper_bound(s_cost.begin(), s_cost.end(), cerch) - s_cost.begin() - 1;
    if (q >= 0) {
      p = s_number[q];
      saved = (n - p) * f_time[i];
      total_saved = min(saved, total_saved);
    } else if (cerch >= 0) {
      total_saved = min(total_saved, n * f_time[i]);
    }
  }
  q = upper_bound(s_cost.begin(), s_cost.end(), b) - s_cost.begin() - 1;
  if (q >= 0) {
    p = s_number[q];
    saved = (n - p) * a;
    total_saved = min(saved, total_saved);
  }
  cout << total_saved << "\n";
  return 0;
}
