q = int(raw_input())
for i in xrange(q):
    n = int(raw_input())
    
    max_x = None
    min_x = None
    max_y = None
    min_y = None
    
    points = []
    for j in xrange(n):
        point = map(int, raw_input().split())
        x, y = point
        
        if max_x is None or x > max_x:
            max_x = x
        
        if min_x is None or x < min_x:
            min_x = x
        
        if max_y is None or y > max_y:
            max_y = y
        
        if min_y is None or y < min_y:
            min_y = y
        
        points.append(point)
    
    answer = 'YES'
    for point in points:
        x, y = point
        
        if x != max_x and x != min_x and y != max_y and y != min_y:
            answer = 'NO'
            break
    
    print answer