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

#define forn(i,n) for (int i=0; i<(n); i++)
#define pb push_back
#define mp make_pair
#define MOD 1000000007
#define f first
#define s second

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll,ll> pll;

template<typename A, typename B> ostream& operator<<(ostream & cout, pair<A,B> const &p) {
    return cout << "("<< p.f << ", "<< p.s << ")";
}
template<typename A> ostream& operator<<(ostream &cout, vector<A> const & v) {
    cout << "[";
    forn(i, v.size()) {
        if(i) cout << ", ";
        cout << v[i];
    }
    return cout << "]";
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
    int t; cin >> t;
    while (t--) {
        int n; cin >> n;
        int a[2*n];
        forn(i, 2*n) cin >> a[i];
        sort(a, a+2*n);
        ll ans = 0;
        forn(i, 2*n) {
            if (i<n) ans -= a[i];
            else ans += a[i];
        }
        cout << ans << '\n';
    }
}