# Enter your code here. Read input from STDIN. Print output to STDOUT
T = int(raw_input())
for t in xrange(T):
    Q = int(raw_input())
    points = []
    for q in xrange(Q):
        points.append(map(int,raw_input().split(' ')))
    lux = 10**6
    luy = -10**6
    rdx = -10**6
    rdy = 10**6
    
    for p in points:
        lux = min(lux,p[0])
        rdx = max(rdx,p[0])
        luy = max(luy,p[1])
        rdy = min(rdy,p[1])
    f = True
    for p in points:
        if p[0] == lux or p[0] == rdx:
            if p[1] > luy or p[1] < rdy:
                f = False
                break
        elif p[1] == luy or p[1] == rdy:
            if p[0] < lux or p[0] > rdx:
                f = False
                break
        else:
            f = False
            break
    if f:
        print "YES"
    else:
        print "NO"