N=int(input())
for i in range(N):
    p=int(input())
    xcor=[]
    ycor=[]
    for j in range(p):
        m,n=[int(x) for x in input().split(' ')]
        xcor.append(m)
        ycor.append(n)
    xmin=min(xcor)
    xmax=max(xcor)
    ymin=min(ycor)
    ymax=max(ycor)
    d=0
    for k in range(len(xcor)):
        if xcor[k]==xmin or xcor[k]==xmax:
            continue
        else:
            if ycor[k]==ymin or ycor[k]==ymax:
                continue
            else:
                d=1
                break
    if d==1:
        print('NO')
    else:
        print('YES')