#include <bits/stdc++.h>
using namespace std;
const long long INF = 1e18;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long n, m, k;
  long long zero = 0;
  cin >> n >> m >> k;
  long long x, s;
  cin >> x >> s;
  long long a[m], b[m], c[k], d[k];
  long long i, j;
  long long ans = n * x;
  for (i = 0; i < m; i++) {
    cin >> a[i];
  }
  for (i = 0; i < m; i++) {
    cin >> b[i];
    if (b[i] <= s) {
      ans = min(ans, n * a[i]);
    }
  }
  for (i = 0; i < k; i++) {
    cin >> c[i];
  }
  for (i = 0; i < k; i++) {
    cin >> d[i];
    if (d[i] <= s) {
      ans = min(ans, x * max(zero, n - c[i]));
    }
  }
  for (i = 0; i < m; i++) {
    if (b[i] <= s) {
      long long p = s - b[i];
      auto it = upper_bound(d, d + k, p);
      if (it != d) {
        it--;
      } else {
        continue;
      }
      long long reduce = c[it - d];
      reduce = min(n, reduce);
      long long temp = (n - reduce) * a[i];
      ans = min(ans, temp);
    }
  }
  cout << ans;
}
