// There is nothing in a caterpillar that tells you its going to be a butterfly --------------------- !
#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define ll  long long int
#define pi pair<int,int>
#define pii pair<ll,pi>
#define f first
#define mp make_pair
#define mod 1000000007
#define s second
#define pb push_back
 
int main(){
    int t;
    cin >> t;
    while(t--){
        ll F,H,W,x;
        cin >> F >> H >> W;
        vector<ll>cuts;
        rep(i,F){
            cin >> x;
            cuts.pb(x);
        }
        cuts.pb(0);
        cuts.pb(W);
        sort(cuts.begin(),cuts.end());
        ll ans=INT_MAX;
        for(int i=1;i<cuts.size();i++){
            ans=min(ans,cuts[i]-cuts[i-1]);
        }
        ans*=H;
        cout<<ans<<"\n";
    }
}
 

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