#include <bits/stdc++.h>
using namespace std;
const int N = 200005;
const int inf = 1000 * 1000 * 1000;
const int mod = 1000 * 1000 * 1000 + 7;
long long n, m, k, mn;
long long x, s;
pair<long long, long long> p[N];
long long a[N], b[N];
int main() {
  scanf("%lld%lld%lld", &n, &m, &k);
  scanf("%lld%lld", &x, &s);
  for (int i = 1; i <= m; i++) scanf("%lld", &p[i].first);
  for (int i = 1; i <= m; i++) scanf("%lld", &p[i].second);
  for (int i = 1; i <= k; i++) scanf("%lld", &a[i]);
  for (int i = 1; i <= k; i++) scanf("%lld", &b[i]);
  p[0].first = x;
  p[0].second = 0ll;
  for (int i = 0; i <= m; i++) {
    long long S = s - p[i].second;
    if (S < 0) continue;
    long long ina = 1, inb = k, answ = 0;
    while (ina <= inb) {
      long long mid = (ina + inb) / 2;
      if (b[mid] <= S) {
        answ = a[mid];
        ina = mid + 1;
      } else
        inb = mid - 1;
    }
    long long sum = (n - answ) * p[i].first;
    if (i == 0 || sum < mn) {
      mn = sum;
    }
  }
  cout << mn << endl;
  return 0;
}
