#include <bits/stdc++.h>
using namespace std;
//long long v[100001];
ifstream f("caluti.in");
ofstream g("caluti.out");
int main()
{unsigned long long t,n,k,p,i,j,z,s=0,sa=0,x,loc=0,y;;
f>>t;
for(i=1;i<=t;i++){
f>>n>>k>>p;
/*for(j=1;j<=n;j++)
    f>>v[j];
j=1;
while(j<=n){
    sa=0;
    for(z=j;z<=k+j-1&&k+j-1<=n;z++){sa=sa+v[z];
                          if(sa+p>v[z+1]){sa=sa-v[z];
                          break;}}
    s=s+sa+p;
    j=j+z;
}
g<<s+p;*/
for(j=1;j<=n;j++){
    f>>x;
    if(s<x){s=s+(x-s);s+=p;}
    else for(z=2;z<=k;z++){f>>y;
    if(s+p>s+y)s=s+(y-s);
    else s=s+p;}
}
g<<s;
}

    return 0;
}