#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    
    int n;
    cin>>n;
    
    while(n != 0){
        int k;
        cin>>k;
        
        vector<int> xs(k);
        vector<int> ys(k);
        
        for(int i=0; i<k; ++i){
            cin>>xs[i]>>ys[i];
        }
        
        int x1,x2,y1,y2;
        x1 = *min_element(xs.begin(),xs.end());
        y1 = *min_element(ys.begin(),ys.end());
        
        x2 = *max_element(xs.begin(),xs.end());
        y2 = *max_element(ys.begin(),ys.end());
          
        /*bool compe = false;
        for(int i=1; i<k; ++i){
             if(xs[i] != x1 && ys[i] != y1){
                    x2 = xs[i];
                    y2 = ys[i];
                 compe = true;
                    break;
            }
        }*/
        
       bool valid = true;
        
        //if(compe){
        for(int i=0; i<k; ++i){
              if((xs[i] != x1 && ys[i] != y1)  && (xs[i] != x2 && ys[i] != y2))
                    {
                    valid = false;
                    break;
                }
            
          /*  else if(xs[i] > max(x1,x2) || xs[i] < min(x1,x2) || ys[i] > max(y1,y2) || ys[i] < min(y1,y2)){
                valid = false;
                    break;
            }*/
        }
        
       // }
        
         if(valid)
            cout<<"YES\n";
        else
            cout<<"NO\n";
     
        
           n--;
    }
        
        
        
  
    return 0;
}