#include<bits/stdc++.h>
using namespace std;
#define int long long
void sol(){
    int n, k;
    cin >> n >> k; 
    int a[n], ans = 0;
    for(int &i:a) cin >> i;
    for(int i = 0; i < n / 2; i++) ans += min(k, abs(a[i] - a[n - i - 1]));
    cout << ans << "\n";
 
}
signed main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    int t = 1;
    cin >> t;
    while(t--){
        sol();
    }
    return 0;
}

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