#!/bin/python

def check(square, xys):
    for xy in xys:
        if xy[0] != square[0]:
            if xy[0] != square[1]:
                return False
        if xy[1] != square[2]:
            if xy[1] != square[3]:
                return False
    return True

def rect(xs,ys,xys):
    for i in xrange(len(xs)-1):
        for j in xrange(i,len(xs)):
            for k in xrange(len(ys)-1):
                for l in xrange(k,len(ys)):
                    square = [xs[i],xs[j],ys[k],ys[l]]
                    if check(square, xys):
                        return True
    return False

q = input()
for _ in xrange(q):
    n = input()
    xs = []
    ys = []
    xys = []
    for i in xrange(n):
        x,y = map(int,raw_input().split())
        if not x in xs:
            xs.append(x)
        if y not in ys:
            ys.append(y)
        xys.append((x,y))
    if rect(xs,ys,xys):
        print "YES"
    else: 
        print "NO"