import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        
		// TODO Auto-generated method stub
		Scanner Sc=new Scanner(System.in);
		int maxy=Integer.MIN_VALUE;
		int maxx=Integer.MIN_VALUE;
		int sumx=0;
		int sumy=0;
		int q=Sc.nextInt();
		int x[]=new int[1000];
		int y[]=new int[1000];
		for(int i=1;i<=q;i++)
		{
			int n=Sc.nextInt();
			for( int j=0;j<n;j++)
			{
				 x[j]=Sc.nextInt();
				 y[j]=Sc.nextInt();
				 sumx=sumx+x[j];
				 sumy=sumy+y[j];
				 
					 if(y[j]>maxy)
					 {
						 maxy=y[j];
					 }
					 if(x[j]>maxx)
					 {
						 maxx=x[j];
					 }
					
			}
			
			int maxsum=maxx+maxy;
			if((sumx+sumy)==(2*maxsum))
			{
				System.out.println("YES");
			}
			else
			{
				System.out.println("NO");
			}
		}

	
    }
}