#include <bits/stdc++.h>
using namespace std;
pair<int, int> cd[200000];
int a[200000], b[200000];
int main(void) {
  int i;
  long long N, M, K, X, S;
  scanf("%lld%lld%lld", &N, &M, &K);
  scanf("%lld%lld", &X, &S);
  for (i = 0; i <= (int)(M)-1; i++) scanf("%d", &a[i]);
  for (i = 0; i <= (int)(M)-1; i++) scanf("%d", &b[i]);
  for (i = 0; i <= (int)(K)-1; i++) scanf("%d", &cd[i].first);
  for (i = 0; i <= (int)(K)-1; i++) scanf("%d", &cd[i].second);
  long long ans = X * N;
  for (i = 0; i <= (int)(M)-1; i++)
    if (b[i] <= S) {
      int rest = S - b[i];
      if (rest < cd[0].second) continue;
      int l, r;
      l = 0;
      r = K;
      while (l + 1 < r) {
        int m = (l + r) / 2;
        if (cd[m].second > rest)
          r = m;
        else
          l = m;
      }
      ans = min(ans, max(0LL, N - cd[l].first) * a[i]);
    }
  for (i = 0; i <= (int)(M)-1; i++)
    if (b[i] <= S) ans = min(ans, N * a[i]);
  for (i = 0; i <= (int)(K)-1; i++)
    if (cd[i].second <= S) ans = min(ans, max(0LL, N - cd[i].first) * X);
  printf("%lld\n", ans);
  return 0;
}
