#include <bits/stdc++.h>
using namespace std;
long long int n, m, k, x, s, x1, s1;
long long int a_short_time[2000003];
long long int a_cost[2000003];
long long int b_pro_num[2000003];
long long int b_cost[2000003];
int main() {
  cin >> n >> m >> k >> x >> s;
  long long int i = 1;
  long long int ans = n * x;
  for (i = 1; i <= m; i++) scanf("%lld", &a_short_time[i]);
  a_short_time[0] = x;
  for (i = 1; i <= m; i++) scanf("%lld", &a_cost[i]);
  a_cost[0] = 0;
  for (i = 1; i <= k; i++) scanf("%lld", &b_pro_num[i]);
  b_pro_num[0] = 0;
  for (i = 1; i <= k; i++) scanf("%lld", &b_cost[i]);
  b_cost[0] = 0;
  for (i = 0; i <= m; i++) {
    if (s >= a_cost[i]) {
      long long int s1 = s - a_cost[i];
      long long int l = 0, r = k;
      while (l < r) {
        long long int mid = (l + r) / 2;
        if (b_cost[mid] <= s1) {
          if (b_cost[mid + 1] > s1) {
            l = mid;
            break;
          } else
            l = mid + 1;
        } else
          r = mid;
      }
      ans = min(ans, a_short_time[i] * (n - b_pro_num[l]));
    }
  }
  printf("%lld", ans);
  return 0;
}
