#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  int m, k;
  scanf("%I64d %d %d", &n, &m, &k);
  long long x, s;
  scanf("%I64d %I64d", &x, &s);
  long long a[m];
  long long b[m];
  for (int i = 0; i < m; ++i) {
    scanf("%I64d", &a[i]);
  }
  for (int i = 0; i < m; ++i) {
    scanf("%I64d", &b[i]);
  }
  long long c[k];
  for (int i = 0; i < k; ++i) {
    scanf("%I64d", &c[i]);
  }
  long long d[k];
  for (int i = 0; i < k; ++i) {
    scanf("%I64d", &d[i]);
  }
  long long res = x * n;
  for (int i = 0; i < m; ++i) {
    if (b[i] <= s) {
      int l = 0, r = k;
      long long price = s - b[i];
      while (l < r) {
        int mid = (l + r) / 2;
        if (d[mid] > price) {
          r = mid;
        } else {
          l = mid + 1;
        }
      }
      long long tot = n;
      if (l - 1 > -1 && d[l - 1] <= price && (l == k || price < d[l])) {
        l--;
      }
      if (l != k && price >= d[l]) {
        tot -= c[l];
      }
      res = min(res, tot * a[i]);
    }
  }
  for (int i = 0; i < k; ++i) {
    if (d[i] <= s) {
      res = min(res, (n - c[i]) * x);
    }
  }
  printf("%I64d", res);
  return 0;
}
