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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */
    int q;
    cin >> q;
    
    while(q--){
        int n;
        cin >> n;
        
        string res = "";
        
        if(n == 1)
            res = "YES";
        else{
            int x1, y1,
                xMin, yMin,
                xMax = INT_MAX, yMax = INT_MAX;
            
            cin >> x1 >> y1;
            xMin = x1;
            yMin = y1;
            n--;
            
            //cout << "xMin: " << xMin << "\tyMin: " << yMin << endl;
            
            while(n--){
                cin >> x1 >> y1;
                
                while(xMax == INT_MAX && yMax == INT_MAX){
                if(x1 > xMin){
                    xMax = x1;
                }else if(x1 < xMin){
                    xMax = xMin;
                    xMin = x1;
                }
                
                if(y1 > yMin){
                    yMax = y1;
                }else if(y1 < yMin){
                    yMax = yMin;
                    yMin = y1;
                }
                }
                
                if(xMax != INT_MAX){
                    if(x1 != xMin && x1 != xMax)
                        res = "NO";
                }
                
                if(yMax != INT_MAX){
                    if(y1 != yMin && y1 != yMax)
                        res = "NO";
                }
                
                //cout << "xMin: " << xMin << "\tyMin: " << yMin << endl;
                //cout << "xMax: " << xMax << "\tyMax: " << yMax << endl;
                
            }//end while
            
            if(res != "NO")
                res = "YES";
            
        }
            cout << res << endl;
    }
    
    return 0;
}