#include <bits/stdc++.h>
using namespace std;
const long long maxn = 200000 + 5;
long long n, m, k, x, s, a[maxn], b[maxn], c[maxn], d[maxn], ans;
signed main() {
  cin.tie(0);
  ios_base::sync_with_stdio(false);
  cin >> n >> m >> k;
  cin >> x >> s;
  for (long long i = 0; i < m; ++i) cin >> a[i];
  for (long long i = 0; i < m; ++i) cin >> b[i];
  for (long long i = 0; i < k; ++i) cin >> c[i];
  for (long long i = 0; i < k; ++i) cin >> d[i];
  ans = n * x;
  for (long long i = 0; i < m; ++i) {
    if (s - b[i] < 0) continue;
    auto it = upper_bound(d, d + k, s - b[i]);
    long long best;
    if (it == d + k)
      best = k - 1;
    else
      best = it - d - 1;
    if (d[best] + b[i] > s) continue;
    long long t = (n - c[best]) * a[i];
    ans = min(ans, t);
  }
  for (long long i = 0; i < m; ++i)
    if (b[i] <= s) ans = min(ans, n * a[i]);
  for (long long i = 0; i < k; ++i)
    if (d[i] <= s) ans = min(ans, x * (n - c[i]));
  cout << ans << '\n';
  return 0;
}
