from math import atan
import math
q = int(input())
    
while q:
    n = int(input())
    X = []
    Y = []
    i = 0
    while i < n:
        x,y = map(int, raw_input().split())
        X.append(x)
        Y.append(y)
        i += 1
    minx = min(X)
    miny = min(Y)
    maxx = max(X)
    maxy = max(Y)
    i = 0
    while i < n:
        x = X[i]
        y = Y[i]
        if x == minx or x == maxx:
            if y < miny or y > maxy:
                print "NO"
                break
        elif y == miny or y == maxy:
            if x < minx or x > maxx:
                print "NO"
                break
        else:
            print "NO"
            break
                
        i += 1
            
    if i == n:
        print "YES"
                
        
    q -= 1