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

#define FOR(i,l,r) for(int i = (l);i < (r);i++)
#define ALL(x) (x).begin(),(x).end()
template<typename T> void chmax(T& a,const T& b){if(a < b) a = b;}
template<typename T> void chmin(T& a,const T& b){if(b < a) a = b;}
typedef long long ll;

int Q;

bool solve()
{
	int N;
	cin >> N;
	vector< pair<int,int> > coor(N);
	set<int> x,y;
	FOR(i,0,N){
		cin >> coor [i].first >> coor [i].second;
		x.insert(coor [i].first);
		y.insert(coor [i].second);
	}

	for(auto a : x){
		for(auto b : x) if(a <= b){
			for(auto c : y){
				for(auto d : y) if(c <= d){
					bool flag = true;
					FOR(i,0,N){
						if((coor [i].first == a || coor [i].first == b) && (c <= coor [i].second && coor [i].second <= d));
						else if((coor [i].second == c || coor [i].second == d) && (a <= coor [i].first && coor [i].first <= b));
						else{
							flag = false;
							break;
						}
					}
					if(flag){
						return true;
					}
				}
			}
		}
	}

	return false;
}

int main()
{
	cin.tie(0);
	ios::sync_with_stdio(false);

	cin >> Q;
	FOR(i,0,Q){
		cout << (solve() ? "YES" : "NO") << endl;
	}

	return 0;
}