#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int,int>;
const int N = 1e6+10;
int t,n,m,k,l,r,op,x,y,ans;
int f[N];
void solve(){
    cin>>t;
    while(t--){
        ans = 0;
        cin>>n;
        for(int i = 0;i<=n;i++){
            cin>>f[i];
        }
        cin>>x;
        for(int i = 0;i<=n;i++){
            ans += f[i] * pow(x,i); 
        }
        cout<<ans<<"\n";
    }
}
int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);  
    solve();
    return 0;
}