def load(q):
    r = []
    for i in range(q):
        x,y = map(int, input().split())
        r.append( (x,y) )
    return r

def solve(pairs):
    right, top = -100000,-100000
    left, bottom = 100000,100000
    for x,y in pairs:
        right = max(right, x)
        top = max(top, y)
        left = min(left, x)
        bottom = min(bottom, y)

    for x,y in pairs:
        if (left < x < right) and (y!=top and y!=bottom):
            return False
        if (bottom < y < top) and (x!=left and x!=right):
            return False
    return True

for _ in range(int(input())):
    print("YES" if solve(load(int(input()))) else "NO")