n = int(input())
for _ in range(n):
    q = int(input())
    points = []
    for __ in range(q):
        points.append([int(x) for x in input().split()])
    ans = True
    if len(points) <= 3:
        ans = True
    else:
        min_x = points[0][0]
        max_x = points[0][0]
        min_y = points[0][1]
        max_y = points[0][1]
        
        for i in range(q):
            if min_x > points[i][0]:
                min_x = points[i][0]
            if min_y > points[i][1]:
                min_y = points[i][1]            
            if max_x < points[i][0]:
                max_x = points[i][0]            
            if max_y < points[i][1]:
                max_y = points[i][1]            
                
        for i in range(q):
            x, y = points[i]
            if x not in [min_x, max_x] and y not in [min_y, max_y]:
                ans = False
                break
    
    if ans:
        print("YES")
    else:
        print("NO")