#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define Fast_IO ios::sync_with_stdio(false);
#define DEBUG fprintf(stderr,"Running on Line %d in Function %s\n",__LINE__,__FUNCTION__)
//mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
#define fir first
#define sec second
#define mod 998244353
#define int long long
#define inf 0x3f3f3f3f
#define INF 0x3f3f3f3f3f3f3f3f
inline int read()
{
	char ch=getchar(); int nega=1; while(!isdigit(ch)) {if(ch=='-') nega=-1; ch=getchar();}
	int ans=0; while(isdigit(ch)) {ans=ans*10+ch-48;ch=getchar();}
	if(nega==-1) return -ans;
	return ans;
}
typedef pair<int,int> pii;
#define N 100005
int a[N],b[N],n;
void work()
{
	cin>>n;
	int c1=0,c2=0;
	for(int i=1;i<=n*2;i++)
	{
		int x=read(),y=read();
		if(!x) a[++c1]=y*y;
		else b[++c2]=x*x;
	}
	sort(a+1,a+n+1),sort(b+1,b+n+1);
	double ans=0;
	for(int i=1;i<=n;i++) ans+=sqrt(a[i]+b[i]);
	printf("%.9lf\n",ans);
}
signed main()
{
	int T=read(); while(T--) work();
	return 0;
}


