for q in range(input()):

    n=input()
    a=[]
    for i in range(n):
        x,y=map(int,raw_input().split())
        a.append([x,y])

    max_x=max([x[0] for x in a])
    min_x=min([x[0] for x in a])
    max_y=max([x[1] for x in a])
    min_y=min([x[1] for x in a])    


    for i in range(n):
        if a[i][0]<>max_x and a[i][0]<>min_x and a[i][1]<>max_y and a[i][1]<>min_y:
            print 'NO'
            break
    else:
        print 'YES'