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

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define F first
#define S second
#define pb push_back
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;

int main() {
	cin.tie(0)->sync_with_stdio(0);
	cin.exceptions(cin.failbit);
	int tests;cin>>tests;
	while(tests--){
		int n;cin>>n;
		vi a(2*n);rep(i,0,2*n)cin>>a[i];
		sort(all(a));
		ll t = 0;
		rep(i,0,n) t+= a[2*n-i-1]-a[i];
		cout<<t<<'\n';
	}
}