UVA_927

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <string>
#include <cctype>
#include <stack>
#include <climits>
#include <bitset>
#include <queue>
#include <list>
#include <vector>
#include <map>
#include <set>
#include <iterator>
#include <sstream>
#include <stdlib.h>
#include <cmath>
#define FOR(i,A) for(typeof (A).begin() i = (A).begin() ; i != (A).end() ; i++)
#define f(i,a,b) for(int i = a ; i < b ; i++)
#define fd(i,a,b) for(int i = a ; i >= b ; i--)
#define debug( x ) cout << #x << " = " << x << endl
#define clr(v,x) memset( v, x , sizeof v )
#define all(x) (x).begin() , (x).end()
#define mp make_pair
#define rall(x) (x).rbegin() , (x).rend()
#define PI acos( -1.0 )
#define EPS 1E-9
#define MAXM 100010
#define MAXN 1000000
using namespace std;

typedef pair<int,int> ii ;
typedef long long ll ;
typedef long double ld ;
typedef pair<int,ii> pii ;
typedef vector <ii> vii;
typedef vector<int> vi;
int seq[MAXN];
int coef[30];
int n;
void pre(){
 int sum=0;
 for(int i=0;;i++){
    sum+=i;
    if(sum>=MAXN) break;
    seq[sum]=i+1;
 }
}
ll eval(int s,int i){
  if(i==n+1) return 0;
  return coef[i]*pow(s,i) + eval(s,i+1);

}
int main() {
    int t,d,k;
    pre();
    scanf("%d",&t);
    f(j,0,t){
        scanf("%d",&n);
        f(i,0,n+1){
            scanf("%d",&coef[i]);
        }
        scanf("%d %d",&d,&k);
        int ind=(k-1)/d;
        while(ind>0 && seq[ind]==0){
            ind--;
        }
        ll gg=eval(seq[ind],0);
        printf("%lld\n",gg);
    }
    return 0;
}