#include <bits/stdc++.h>
using namespace std;
const int N = 200200;
unsigned long long n;
int m, k;
unsigned long long x, s;
unsigned long long a[N], b[N];
unsigned long long c[N], d[N];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cin >> n >> m >> k;
  cin >> x >> s;
  for (int i = (int)0; i < (int)m; ++i) cin >> a[i];
  for (int i = (int)0; i < (int)m; ++i) cin >> b[i];
  for (int i = (int)0; i < (int)k; ++i) cin >> c[i];
  for (int i = (int)0; i < (int)k; ++i) cin >> d[i];
  d[k] = (unsigned long long)2e9 + 1;
  unsigned long long t = (n - c[upper_bound(d, d + k, s) - d - 1]) * x;
  for (int i = (int)0; i < (int)m; ++i) {
    if (b[i] > s) continue;
    unsigned long long v = s - b[i];
    unsigned long long ans = 0;
    int idx = upper_bound(d, d + k + 1, v) - d;
    if (idx) {
      if (d[idx] > v) --idx;
      ans = a[i] * (n - c[idx]);
    } else {
      if (d[idx] > v)
        ans = a[i] * n;
      else
        ans = a[i] * (n - c[idx]);
    }
    t = min(t, ans);
  }
  cout << t;
  return 0;
}
