def main():
    for i in range(int(input())):
        p = [list(map(int, input().split())) for j in range(int(input()))]
        px, py = zip(*p)
        x0 = min(px)
        x1 = max(px)
        y0 = min(py)
        y1 = max(py)
        result = all(x in (x0, x1) or y in (y0, y1) for x, y in p)
        print("YES" if result else "NO")

main()