#include <bits/stdc++.h>
using namespace std;
long long a[222222], b[222222], c[222222], d[222222];
set<long long> st;
set<long long>::iterator it;
map<long long, long long> sp2;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long n, m, k, x, s, i;
  cin >> n >> m >> k;
  cin >> x >> s;
  for (i = 1; i <= m; i++) {
    cin >> a[i];
  }
  for (i = 1; i <= m; i++) {
    cin >> b[i];
  }
  for (i = 1; i <= k; i++) {
    cin >> c[i];
  }
  for (i = 1; i <= k; i++) {
    cin >> d[i];
    st.insert(d[i]);
    sp2[d[i]] = c[i];
  }
  long long ans = n * x;
  long long rem;
  long long temp;
  for (i = 1; i <= m; i++) {
    if (b[i] <= s) {
      temp = 0;
      rem = s - b[i];
      it = st.upper_bound(rem);
      if (it != st.begin()) {
        it--;
        temp += sp2[*it];
      }
      if (temp >= n)
        ans = 0;
      else
        ans = min(ans, (n - temp) * a[i]);
    }
  }
  temp = 0;
  it = st.upper_bound(s);
  if (it != st.begin()) {
    it--;
    temp += sp2[*it];
  }
  if (temp >= n)
    ans = 0;
  else
    ans = min(ans, (n - temp) * x);
  cout << ans << endl;
  return 0;
}
