# Enter your code here. Read input from STDIN. Print output to STDOUT
for _ in range(input()):
    q = input()
    if q <= 2:
        print 'YES'
        for _ in range(q):
            raw_input()
        continue
        
    res = 'YES'
    points = []
    for _ in range(q):
        (x, y) = map(int, raw_input().split())
        points.append((x, y))
        
    xMin = min([x for (x,y) in points])
    yMin = min([y for (x,y) in points])
    xMax = max([x for (x,y) in points])
    yMax = max([y for (x,y) in points])
    for (x, y) in points:
        if (xMin < x < xMax) and (yMin < y < yMax):
            res = 'NO'
    print res