#include <bits/stdc++.h>
using namespace std;
int tu(int val) { return (1 << val); }
bool iset(int mask, int id) {
  if ((mask & tu(id)) != 0) return true;
  return false;
}
void doset(int &mask, int id) { mask |= tu(id); }
void dounset(int &mask, int id) { mask = mask & (~tu(id)); }
template <typename T>
string tos(T a) {
  stringstream ss;
  string ret;
  ss << a;
  ss >> ret;
  return ret;
}
const int LM = 200007;
long long s, A[LM], B[LM], C[LM], D[LM];
long long n, x;
struct nd {
  long long cost, rate;
  bool operator<(const nd &T) const {
    if (cost != T.cost)
      return cost < T.cost;
    else
      return rate > T.rate;
  }
};
vector<nd> arr;
int main() {
  int m, k;
  while (cin >> n >> m >> k) {
    arr.clear();
    cin >> x >> s;
    for (int(i) = (0); (i) < (m); (i)++) scanf("%I64d", &A[i]);
    for (int(i) = (0); (i) < (m); (i)++) scanf("%I64d", &B[i]);
    for (int(i) = (0); (i) < (k); (i)++) scanf("%I64d", &C[i]);
    for (int(i) = (0); (i) < (k); (i)++) scanf("%I64d", &D[i]);
    long long ans = n * x;
    for (int(i) = (0); (i) < (m); (i)++) {
      if (B[i] <= s) {
        long long cst = (long long)n * (long long)A[i];
        if (cst < ans) ans = cst;
      }
    }
    for (int(i) = (0); (i) < (k); (i)++) {
      if (D[i] <= s) {
        long long nw = n - C[i];
        if (nw < 0) nw = 0;
        long long cst = (long long)nw * (long long)x;
        if (cst < ans) ans = cst;
      }
    }
    for (int(i) = (0); (i) < (m); (i)++) {
      nd nw;
      nw.cost = B[i];
      nw.rate = A[i];
      arr.push_back(nw);
    }
    sort(arr.begin(), arr.end());
    int bind = k - 1;
    for (int(i) = (0); (i) < (m); (i)++) {
      A[i] = arr[i].rate;
      B[i] = arr[i].cost;
      while (bind >= 0 && B[i] + D[bind] > s) {
        bind--;
      }
      if (bind >= 0) {
        long long nw = n - C[bind];
        if (nw < 0) nw = 0;
        long long cst = (long long)nw * (long long)A[i];
        if (cst < ans) ans = cst;
      }
    }
    if (ans < 0) ans = 0;
    cout << ans << endl;
  }
  return 0;
}
