import java.util.*;
class rectangle
{
    public static void main(String args[])
    {
        Scanner ex=new Scanner(System.in);
        int q=ex.nextInt();
        while(q-->0)
        {
            int n=ex.nextInt();
            int arr[][]=new int[2][n];
            arr[0][0]=ex.nextInt();
            arr[1][0]=ex.nextInt();
            int x1=100000,x2=100000,y1=100000,y2=100000;
            int flag=0;
            for(int i=1;i<n;i++)
            {
                arr[0][i]=ex.nextInt();
                arr[1][i]=ex.nextInt();
            }
            for(int i=0;i<n;i++)
            {
                int x=arr[0][i];
                int y=arr[1][i];
                int countx=0,county=0;
                for(int j=i;j<n;j++)
                {
                    if(arr[0][j]==x)
                    countx++;
                    if(arr[1][j]==y)
                    county++;
                }
                if(countx>1&&x!=x1&&x!=x2)
                {
                    if(x1==100000)
                    x1=x;
                    else if(x2==100000)
                    x2=x;
                    else
                    {
                        flag=1;
                        break;
                    }
                }
                if(county>1&&y!=y1&&y!=y2)
                {
                    if(y1==100000)
                    y1=y;
                    else if(y2==100000)
                    y2=y;
                    else
                    {
                        flag=1;
                        break;
                    }
                }
            }
            for(int i=0;i<n;i++)
            {
                if(arr[0][i]==x1||arr[0][i]==x2)
                continue;
                else if(arr[1][i]==y1||arr[1][i]==y2)
                continue;
                else if(n>2)
                {
                    flag=1;
                    break;
                }
            }
            if(flag==1)
            System.out.println("NO");
            else
            System.out.println("YES");
        }
    }
}