q = int(input())
for i in range(q):
    n = int(input())
    a = []
    a.append(tuple(map(int,input().split())))
    xmin = a[0][0]
    xmax = a[0][0]
    ymin = a[0][1]
    ymax = a[0][1]
    a = []
    for j in range(n-1):
        a.append(tuple(map(int,input().split())))
        if a[j][0] < xmin:
            xmin = a[j][0]
        if a[j][0] > xmax:
            xmax = a[j][0]
        if a[j][1] < ymin:
            ymin = a[j][1]
        if a[j][1] > ymax:
            ymax = a[j][1]
    answer = 'YES'
    for j in a:
        if (xmin <= j[0] <= xmax and (j[1] == ymin or j[1] == ymax)) or (ymin <= j[1] <= ymax and (j[0] == xmin or j[0] == xmax)):
            continue
        else:
            answer = 'NO'
            break
    print(answer)