A

#include <bits/stdc++.h>

using namespace std;

int main() {
    int t;
    cin>>t;

    while(t--){
        int n;
        cin>>n;

        vector<int> v(2*n);
        for(auto &e: v)     cin>>e;

        sort(v.begin(), v.end());

        int ans = 0;

        for(int i=0; i<2*n; i+=2)
            ans += v[i];

        cout<<ans<<"\n";
    }
}