# Enter your code here. Read input from STDIN. Print output to STDOUT
Q = input()
for q in range(Q):
    n = input()
    x = []
    y = []
    for i in range(n):
        xx, yy = map(int, raw_input().split())
        x.append(xx)
        y.append(yy)
    mx = min(x)
    my = min(y)
    Mx = max(x)
    My = max(y)
    sirve = True
    for i in range(n):
        if x[i] not in (mx, Mx) and y[i] not in (my, My):
            sirve = False
    if sirve:
        print "YES"
    else:
        print "NO"