#include<bits/stdc++.h>
bool Mbg;
using namespace std;
#define vec vector
#define pb push_back
#define eb emplace_back
#define siz(vec) ((int)(vec).size())
#define all(vec) (vec).begin(),(vec).end()
template<class T>
void operator +=(vec<T> &a,T b){a.push_back(b);}
template<class T>
void operator --(vec<T> &a){a.pop_back();}
#define pii pair<int,int>
#define x first
#define y second
#define mp make_pair
#define exc(exp) if(exp)continue;
#define stop(exp) if(exp)break;
#define ret(exp) if(exp)return;
#define deb(var) cerr<<#var<<'='<<(var)<<"; "
#define debl(var) cerr<<#var<<'='<<(var)<<";\n"
#define ins insert
#define era erase
#define lb lower_bound
#define ub upper_bound
#define int long long
#define inf (long long)(1e18)
template<class T>
bool Min(T &x,T y){return x>y?x=y,1:0;}
template<class T>
bool Max(T &x,T y){return x<y?x=y,1:0;}
const int mod=998244353;
void Add(int &x,int y){x=x+y<mod?x+y:x+y-mod;}
void Dec(int &x,int y){x=x>=y?x-y:x-y+mod;}
int fpm(int x,int y){
    int ans=1;for(;y;y>>=1,x=1ll*x*x%mod)if(y&1)ans=1ll*x*ans%mod;return ans;
}

int n,m,k,c,a[500010],s[500010],f[500010];
void work(){
    cin>>n>>m>>k>>c;
    for(int i=1;i<=n;i++){
        cin>>a[i];
        s[i]=s[i-1]+a[i];
    }

    f[n+1]=0;
    for(int i=n;i;i--){
        f[i]=f[i+1]+a[i];

        int lst=0,rem=0;
        for(int j=i;j<=n;j++){
            // [i,j] clearable

            if(a[j]+rem<k){
                if(!rem)lst=j;
                rem+=a[j];
            }else{
                int r=a[j]-(k-rem);
                
                if(j-lst+1>m){
                    break;
                }

                rem=r%k;lst=j;
            }
            if(rem&&j-lst+1>m){
                break;
            }

            Min(f[i],f[j+1]+(s[j]-s[i-1]+k-1)/k*c);
            Min(f[i],f[j+1]+(s[j]-s[i-1])/k*c+(s[j]-s[i-1])%k);
        }
    }

    cout<<f[1]<<'\n';
}
bool Med;
signed main(){
    ios::sync_with_stdio(0),
    cin.tie(0),cout.tie(0);
    int T=1;cin>>T;while(T--)work();
    // cerr<<"Time: "<<clock()<<" ms;\n";
    // cerr<<"Memory: "<<abs(&Med-&Mbg)/1024.0/1024.0<<" MiB.\n";
}
/*
- CONTINUE, NON-STOPPING, FOR THE FAITH
- START TYPING IF YOU DON'T KNOW WHAT TO DO
- STOP TYPING IF YOU DON'T KNOW WHAT YOU'RE DOING
*/