#include <bits/stdc++.h>
using namespace std;

void solve()
{
	double a, d, c, p, n;
	cin >> a >> d >> c >> p >> n;
	//ct^2 + (2d + c)t - 2(n-a) = 0
	double D = (2.0*d + c) * (2.0*d + c) + 8.0 * (n-a) * c;
	double T = sqrt(D) - (2.0*d + c);
	T /= (2.0*c);
	cout << max(0, (int)(ceil(T) * p)) << endl;
}

int main()
{
	int t;
	cin >> t;
	while (t--)
		solve();
	return 0;
}