import java.io.*;
import java.util.*;

public class Solution {
    
    private static boolean rect(int[] x, int[] y, int n) {
        if (n < 3) {
            return true;
        }
        
        
        int minX = x[0];
        int maxX = x[0];
        int minY = y[0];
        int maxY = y[0];
        for (int i = 1; i < n; i++) {
            minX = Math.min(minX, x[i]);
            minY = Math.min(minY, y[i]);
            maxX = Math.max(maxX, x[i]);
            maxY = Math.max(maxY, y[i]);
        }
        
        
        for (int i = 0; i < n; i++) {
            boolean b = false;
            if ((x[i] == minX || x[i] == maxX) && (y[i] >= minY && y[i] <= maxY)) {
                b = true;
            }
            if ((y[i] == minY || y[i] == maxY) && (x[i] >= minX && x[i] <= maxX)) {
                b = true;
            }
            if (!b) {
                return false;
            }
        }
        
        return true;
    }

    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        Scanner sc = new Scanner(System.in);
        int t = sc.nextInt();
        while(t-- > 0) {
            int n = sc.nextInt();
            int[] x = new int[n];
            int[] y = new int[n];
            for (int i = 0; i < n; i++) {
                x[i] = sc.nextInt();
                y[i] = sc.nextInt();
            }
            System.out.println(rect(x, y, n) ? "YES" : "NO");
        } 
    }
}