#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
struct points
    {
    int x,y;
}p[10],m[10];
int main() {
    int t,q,a[10],f,i,j,k,x,y,r_s,b_s,l_s,u_s;
    scanf("%d",&t);
    while(t--)
        {
        k=0,f=0,r_s=-1,b_s=-1,u_s=-1,l_s=-1;
        scanf("%d",&q);
        for(i=0;i<q;i++)
            { 
            scanf("%d %d",&p[i].x,&p[i].y);
        }
        l_s=p[0].x , b_s=p[0].y,f=0;
        for(i=1;i<q;i++)
            {
            if(p[i].x!=l_s && p[i].x!=r_s)
                {
                if(r_s==-1)
                    {
                    r_s=p[i].x;
                }
                else
                    {
                    f=1;
                    break;
                }
                if(p[i].y!=u_s && p[i].y!=b_s)
                    {
                    if(u_s==-1)
                        u_s=p[i].y;
                    else
                    {
                    f=1;
                    break;
                }
                }
            }
            else
                {
                if(p[i].x==l_s)
                    {
                    if(u_s==-1)
                        u_s=p[i].y;
                }
            }
        }
        if(f==1)
            printf("NO\n");
        else
            printf("YES\n");
    }
        
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */    
    return 0;
}