# Enter your code here. Read input from STDIN. Print output to STDOUT
q = input()
for i in range(q):
    n = input()
    ax = [0]*n
    ay = [0]*n
    flag = True
    for j in range(n):
        x, y = map(int, raw_input().split())
        ax[j] = x
        ay[j] = y
    minx = min(ax)
    maxx = max(ax)
    for x in ax:
        if not (x == minx or x == maxx):
            flag = False
    miny = min(ay)
    maxy = max(ay)
    for y in ay:
        if not (y == miny or y == maxy):
            flag = False
    if flag:
        print 'YES'
    else:
        print 'NO'