#include<bits/stdc++.h>
using namespace std;
int a[500005];
long long S[500005];
long long f[500005];
int R[500005];
int sm[15000005],ls[15000005],rs[15000005],tot=0;
void fuzhi(int l,int r,int o,int ll,int rr,int z){
	if(l>=ll&&r<=rr){
		sm[o]=min(sm[o],z);
		return;
	}
	int mid=(l+r)>>1;
	if(mid>=ll){
		if(!ls[o])ls[o]=++tot,sm[tot]=1e9;
		fuzhi(l,mid,ls[o],ll,rr,z);
	}
	if(mid<rr){
		if(!rs[o])rs[o]=++tot,sm[tot]=1e9;
		fuzhi(mid+1,r,rs[o],ll,rr,z);
	}
}
int qiu(int l,int r,int o,int x){
	if(!o)return 1e9;
	if(l==r)return sm[o];
	int mid=(l+r)>>1,ans=sm[o];
	if(x<=mid)ans=min(ans,qiu(l,mid,ls[o],x));
	else ans=min(ans,qiu(mid+1,r,rs[o],x));
	return ans;
}
int n,m,k,c;
long long s1[15000005],s2[15000005];
vector<int>g[500005];
void add(int l,int r,int o,int x,long long t1,long long t2){
	if(l==r){
		s1[o]=min(s1[o],t1);s2[o]=min(s2[o],t2);
		return;
	}
	int mid=(l+r)>>1;
	if(x<=mid){
		if(!ls[o])ls[o]=++tot,s1[tot]=s2[tot]=1e18;
		add(l,mid,ls[o],x,t1,t2);
		s1[o]=min(s1[o],s1[ls[o]]);
		s2[o]=min(s2[o],s2[ls[o]]);
	}else{
		if(!rs[o])rs[o]=++tot,s1[tot]=s2[tot]=1e18;
		add(mid+1,r,rs[o],x,t1,t2);
		s1[o]=min(s1[o],s1[rs[o]]);
		s2[o]=min(s2[o],s2[rs[o]]);
	}
}
long long m1,m2;
void query(int l,int r,int o,int ll,int rr){
	if(!o)return;
	if(l>=ll&&r<=rr){
		m1=min(m1,s1[o]);m2=min(m2,s2[o]);
		return;
	}
	int mid=(l+r)>>1;
	if(mid>=ll)query(l,mid,o<<1,ll,rr);
	if(mid<rr)query(mid+1,r,o<<1|1,ll,rr);
}
void solve(int l,int r){
	if(l==r)return;
	int mid=(l+r)>>1;
	solve(mid+1,r);
	for(int i=1;i<=tot;++i)ls[i]=rs[i]=0;
	tot=1;s1[tot]=s2[tot]=1e18;
	for(int i=mid+1;i<=r;++i)g[i].clear();
	for(int i=l;i<=mid;++i)if(R[i]>=mid+1){
		g[min(r,R[i])].emplace_back(i);
	}
	for(int j=mid+1;j<=r;++j){
		add(0,k-1,1,S[j]%k,f[j]+S[j]/k*c,f[j]+S[j]/k*c+S[j]%k);
		for(auto i:g[j]){
			if(S[i]%k>0){
				m1=m2=1e18;
				query(0,k-1,1,0,S[i]%k-1);
				f[i]=min(f[i],m1-S[i]/k*c);
				f[i]=min(f[i],m2-S[i]/k*c-c+k-S[i]%k);
			}
			if(S[i]%k<k){
				m1=m2=1e18;
				query(0,k-1,1,S[i]%k,k-1);
				f[i]=min(f[i],m1-S[i]/k*c+c);
				f[i]=min(f[i],m2-S[i]/k*c-S[i]%k);
			}
		}
	}
	solve(l,mid);
}
int main(){
	int T;
	scanf("%d",&T);
	while(T--){
		scanf("%d%d%d%d",&n,&m,&k,&c);
		for(int i=1;i<=n;++i)scanf("%d",&a[i]),S[i]=S[i-1]+a[i];
		if(m==1){
			long long ans=0;
			for(int i=1;i<=n;++i){
				ans+=1ll*a[i]/k*c;
				ans+=min(c,a[i]%k);
			}
			printf("%lld\n",ans);
			continue;
		}
		for(int i=0;i<=n;++i)f[i]=1e18;
		f[n]=0;
		for(int i=1;i<=tot;++i)sm[i]=ls[i]=rs[i]=0;
		tot=1;sm[1]=n;
		for(int i=n;i>=1;--i){
			if(i+m<=n){
				int j=i+m;
				long long z=k+S[j-m]-S[j-1]-1;
				if(z>=0){
					int L=(S[j-m]-z)%k,R=S[j-m]%k;
					if(L<0)L+=k;
					if(R<0)R+=k;
					if(L<=R){
						fuzhi(0,k-1,1,L,R,j-1);
					}else{
						fuzhi(0,k-1,1,L,k-1,j-1);
						fuzhi(0,k-1,1,0,R,j-1);
					}
				}
			}
			R[i-1]=qiu(0,k-1,1,S[i-1]%k);
		}
		solve(0,n);
		printf("%lld\n",f[0]);
	}
	return 0;
}