#include<iostream>
#include<vector>
using namespace std;
class poly{
private:
	vector<int> vint;
	int x;
	int N;
	int ans;
public:
	poly(){}
	~poly(){}
	void in();
	int out(int i);
};
void poly::in()
{
	int num;
	cin >> N;
	for (int i = 0; i <= N; i++) {
		cin >> num;
		vint.push_back(num);
	}
	cin >> num;
	x = num;
	ans = 1;
}
int poly::out(int i)
{
	if (i == 0)
		return ans*vint[i] + out(i+1);
	else if (i == N) {
		ans *= x;
		return ans*vint[i];
	}
	else {
		ans *= x;
		return ans*vint[i] + out(i+1);
	}
}
int main()
{
	int m;
	cin >> m;
	while (m--) {
		poly p;
		p.in();
		cout << p.out(0) << endl;
	}
	return 0;
}