#include <bits/stdc++.h>
#define ld long double
#define ll long long
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define ff first
#define ss second
#define no cout << "NO\n";
#define yes cout << "YES\n";
#define imp cout << "-1\n";
#define nl cout << "\n";
#define sp << " "
#define lb lower_bound
#define ub upper_bound
#define ull unsigned long long
#define MOD 1000000007
#define INF LONG_LONG_MAX
#define MINF LONG_LONG_MIN
#define PI 3.141592653589793
using namespace std;

// #######################

void solve(){
	int n,i,x,y;
	cin>>n;
	vector<int> v1,v2;
	ld ans=0;
	for(i=0;i<2*n;i++){
		cin>>x>>y;
		if(x==0)
			v1.pb(abs(y));
		else
			v2.pb(abs(x));
	}
	sort(v1.begin(),v1.end());
	sort(v2.begin(),v2.end());
	for(i=0;i<n;i++){
		ans+=sqrt(1LL*v1[i]*v1[i]+1LL*v2[i]*v2[i]);
	}	cout<<fixed<<setprecision(10)<<ans; nl
    return;
}

// #######################
	signed main()
	{
ios_base::sync_with_stdio(false); 
cin.tie(0),cout.tie(0);
srand(time(NULL));

		ll t = 1;
	   cin >> t;
		while (t--)
			solve();
	}