for _ in xrange(int(input())):
    n = int(input())
    xs = []
    ys = []
    for i in xrange(n):
        x, y = map(int, raw_input().split())
        xs.append(x)
        ys.append(y)
    lx, rx, ly, ry = min(xs), max(xs), min(ys), max(ys)
    good = True
    for i in xrange(n):
        if lx < xs[i] < rx and ys[i] != ly and ys[i] != ry:
            good = False
        if ly < ys[i] < ry and xs[i] != lx and xs[i] != rx:
            good = False
    print "YES" if good else "NO"