#include <bits/stdc++.h>
using namespace std;
const int MAX = 200005;
int a[MAX], b[MAX], c[MAX], d[MAX];
int main() {
  int n, m, k, x, s, cur, tmp;
  scanf("%d%d%d%d%d", &n, &m, &k, &x, &s);
  long long ans = 1ll * x * n;
  a[0] = x, b[0] = 0;
  for (int i = 1; i <= m; i++) scanf("%d", a + i);
  for (int i = 1; i <= m; i++) scanf("%d", b + i);
  for (int i = 0; i < k; i++) scanf("%d", c + i);
  for (int i = 0; i < k; i++) scanf("%d", d + i);
  for (int i = 0; i <= m; i++) {
    if (b[i] > s) continue;
    cur = s - b[i];
    ans = min(ans, 1ll * a[i] * n);
    int j = upper_bound(d, d + k, cur) - d - 1;
    if (j >= 0) {
      tmp = n - c[j];
      ans = min(ans, 1ll * a[i] * tmp);
    }
  }
  printf("%I64d\n", ans);
  return 0;
}
