#include <bits/stdc++.h>
using namespace std;
#define ll long long int
#define ull unsigned long long int 
#define ld long double
#define f(i,n) for(ll i=0;i<n;i++)
#define f1(i,n) for(ll i=1;i<=n;i++)
#define f11(i,a,n,b) for(ll i=a;i<=n;i+=b)
#define fa(x,m) for(auto x:m)
#define fa1(a) for( auto itr=a.begin();itr!=a.end();itr++)
#define o(n) cout<<n<<endl
#define speed ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define sp(n,val) cout<<fixed<<setprecision(n)<<val<<endl;
#define Tc ll t;cin>>t;while(t--)
#define yes cout<<"yes"<<"\n"
#define no cout<<"no"<<"\n"
#define No cout<<"No"<<"\n"
#define Yes cout<<"Yes"<<"\n"
#define NO cout<<"NO"<<"\n"
#define YES cout<<"YES"<<"\n"
#define vl vector<ll>
#define vp vector< pair<ll,ll>> 
#define vs vector <string> 
#define vc vector <char>
#define pb push_back
#define ppb(a,b) push_back(make_pair(a,b))
#define in(a,n); ll a[n]; for(ll i=0;i<n;i++) {cin>>a[i];}
#define out(a,n); for(ll i=0;i<n;i++) {cout<<a[i]<<" ";} cout<<endl;
#define mll map<ll,ll>
#define mcl map<char,ll>
#define msl map<string,ll>
#define ff first
#define ss second
#define pi 3.1415926535897932
#define all(a) (a).begin(), (a).end()

bool sortbyfir(const pair<int,int> &a , const pair<int,int> &b)
{
    if(a.first == b.first)  return a.second < b.second;
    return a.first < b.first;
}

bool sortbysec(const pair<int,int> &a,const pair<int,int> &b) 
{ 
    if(a.second==b.second) return b.first>a.first;
    return (a.second < b.second); 
}

bool compmx(int a, int b) {return (a < b);}

ll binaryToDecimal(string n)
{
	string num = n;
	ll dec_value = 0;
	ll base = 1;
	for (int i = num.length() - 1; i >= 0; i--) {
		if (num[i] == '1')
			dec_value += base;
		base = base * 2;
	}
	return dec_value;
}

ll bin(ll n) 
{ 
    ll B_Number = 0; 
    ll c=1; 
    while (n != 0) { 
        ll rem = n % 2; 
        B_Number += rem * c; 
        c*=10;
        n /= 2;  
    } 
    return B_Number; 
} 

ll gcd(ll a, ll b)
{
    if (b == 0) return a;
    else return gcd(b, a % b);
}

bool is_prime(ll x) {

    if(x==1) return false;
    if(x==2 || x==3) return true;

    for(ll i=2;i*i<=x;i++)
    {
        if(x%i==0) return false;
    }
    return true;
}
ull fact(ull n)
{
    if (n == 0) return 1;
    return n * fact(n - 1);
}

int main()
{
    speed;
    Tc
    {
        ll n;
        cin>>n;

        ll x,y;
        vl miner,mine;

        f(i,2*n)
        {
            cin>>x>>y;

            if(x==0) miner.pb(abs(y));
            else mine.pb(abs(x));
        }

        sort(all(mine));
        sort(all(miner));

        ld ans=0;

        f(i,n)
        {
            ans+= sqrt(1.0*(miner[i]*miner[i]+mine[i]*mine[i]));
        }

         cout << fixed << setprecision(10) << ans << endl; 
    }

    return 0;
}
    
 