#!/bin/python

import sys

q = int(raw_input().strip())

for q_ in range(q):
    n = int(raw_input().strip())
    p = {'x': [], 'y': []}
    for n_ in range(n):
        point = map(int, raw_input().strip().split(' '))
        p['x'].append(point[0])
        p['y'].append(point[1])
    
    x = [min(p['x']), max(p['x'])]
    y = [min(p['y']), max(p['y'])]
    
    rect = True
    for i in range(len(p['x'])):
        if p['x'][i] not in x and p['y'][i] not in y:
            rect = False
    
    print 'YES' if rect else 'NO'