using System;
using System.Collections.Generic;
using System.IO;

class Solution {
    public class PointXY 
    {
        public int X;
        public int Y;
    }

    static void Main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution */

        List<PointXY> pl = new List<PointXY>();

        int q = Int32.Parse(Console.ReadLine());

        for (int qi=0; qi<q; qi++)
        {
            string result = "YES";
            pl.Clear();

            int n = Int32.Parse(Console.ReadLine());

            for (int ni=0; ni<n; ni++)
            {
                int[] xy = Array.ConvertAll(Console.ReadLine().Split(' '), Int32.Parse);            
                pl.Add(new PointXY() { X=xy[0], Y=xy[1]});
            }

            PointXY p1 = pl[0];
            PointXY p2 = null;
            for (int i=1; i<n; i++)            
            {
                if ((pl[i].X == p1.X) || (pl[i].Y == p1.Y)) continue;
               

                if (p2 != null)
                {
                    result = "NO";
                    break;
                } else                     
                {
                    p2 = pl[i];
                }
            }
            
            int minX = 0;
            int maxX = 0;
            int minY = 0;
            int maxY = 0;            
            if (p2 != null)
            {
                minX = Math.Min(p1.X, p2.X);
                maxX = Math.Max(p1.X, p2.X);
                minY = Math.Min(p1.Y, p2.Y);
                maxY = Math.Max(p1.Y, p2.Y);
            }
            
            if (result == "YES")
            {
                for (int i=1; i<n; i++)            
                {
                    if (pl[i] == p2) continue;

                    if (((pl[i].X == p1.X) || (pl[i].Y == p1.Y)) && (p2 == null)) continue;
                        
                    if ((p2 != null) && 
                        ((((pl[i].X == p1.X) || (pl[i].X == p2.X)) && (pl[i].Y >= minY) && (pl[i].Y <= maxY))
                        || ((pl[i].Y == p1.Y) || (pl[i].Y == p2.Y)) && (pl[i].X >= minX) && (pl[i].X <= maxX))) continue;

                    result = "NO";
                    break;
                }
            }
            
            Console.WriteLine(result);
        }
    }
}