#include<bits/stdc++.h>
#define int long long
using namespace std;

const int N = 2e5 + 5;

int n,k,l,x;
int a[N],b[N];

bool cmp(int u,int v) {
    return u > v;
}

signed main()
{
    freopen("fly.in","r",stdin);
    freopen("fly.out","w",stdout);
    ios::sync_with_stdio(0);
    cin.tie(0);
    int T;cin>>T;
    while(T--){
        cin>>n>>k>>l;
        for(int i = 1;i <= n;i++) cin>>a[i];
        sort(a + 1,a + 1 + n);
        
        for(int i = 1;i < n;i++) b[i] = a[i + 1] - a[i];
        sort(b + 1 ,b + n,cmp);
        
        int ans = 0,pre = 0,kk;
        for(int i = 0;i <= min(n - 1,k);i++){
            pre += b[i] / 2;kk = k - i;
            if(kk) ans = max(ans,2 * pre + max(a[1],l - a[n]) + (kk - 1) * (a[1] + l - a[n] + 2 * pre));
        }
        
        cout<<ans<<'\n';
    }    
    
    return 0;
 }