#include <iostream>
#include <stdio.h>
#include <stack>
#include <vector>
#include <algorithm>
using namespace std;

#define pb push_back
#define mp make_pair

typedef long long ll;
typedef long double ld;
#define sz(v) (int)v.size()

ll INF = 1ll << 50;
const int N = 1000002;

int t,n;
ll a,b,c,x[N],dp[N],A[N];
ll k1[N],b1[N];

/////////////////////// convex hull trick: begin
struct line{
    ll k,b;
    ll xs;
    line(ll k1, ll b1){
        k = k1;
        b = b1;
        xs = -INF;
    }
};
struct chull{
    vector <line> v;

    void add(ll k, ll b){
        line L(k,b);
        while(!v.empty()){
            line R = v.back();
            ll x = ((R.b - L.b) + (L.k - R.k) - 1)/(L.k - R.k);
            if(x <= R.xs) v.pop_back();
            else {L.xs = x; break;}
        }
        v.push_back(L);
    }
    ll get(ll x){
        int B = 0, E = sz(v)-1;
        while(B!=E){
            int M = (B+E+1)/2;
            if(v[M].xs > x) E = M-1;
            else B = M;
        }
        return x*v[B].k + v[B].b;
    }
};
/////////////////////// convex hull trick: end

int main(){
    scanf("%d", &t);
    while(t){
        t--;
        scanf("%d", &n);
        scanf("%lld%lld%lld", &a, &b, &c);
        chull st;
        for(int i=1;i<=n;i++){
            scanf("%lld", &x[i]);
            A[i] = A[i-1] + x[i];
            k1[i] = -2*a*A[i];
        }
        dp[1] = a*x[1]*x[1] + b*x[1] + c;
        b1[1] = dp[1] + a*A[1]*A[1] - b*A[1];
        st.add(k1[1], b1[1]);
        for(int i=2;i<=n;i++){
            dp[i] = a*A[i]*A[i] + b*A[i] + c + st.get(A[i]);
            dp[i] = max(dp[i],a*A[i]*A[i] + b*A[i] + c);
            b1[i] = dp[i] + a*A[i]*A[i] - b*A[i];
            st.add(k1[i], b1[i]);
        }
        printf("%lld\n", dp[n]);
    }
    return 0;
}