#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 7;
typedef long long ll;
ll a[N], b[N], c[N], d[N];
int n, m, k, x, s;
int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin >> n >> m >> k >> x >> s;
	for (int i = 0; i < m; ++i)
		cin >> a[i];
	for (int i = 0; i < m; ++i)
		cin >> b[i];
	for (int i = 1; i <= k; ++i)
		cin >> c[i];
	for (int i = 1; i <= k; ++i)
		cin >> d[i];
	int tmp = upper_bound(d + 1, d + k + 1, s) - d;
	ll ans = (n - c[tmp - 1]) * x;
	for (int i = 0; i < m; ++i)
		if (b[i] <= s) {
			tmp = upper_bound(d + 1, d + k + 1, s - b[i]) - d;
			ans = min(ans, (n - c[tmp - 1]) * a[i]);
		}
	cout << ans << endl;
	return 0;
}