q= int(input())
for _ in range(q):
    i=int( input() )
    distinct = {}
    points=[]
    xmax,xmin,ymax,ymin=-999999,999999,-999999,999999
    for i in range(i):
        x,y = list(map(int, input().split()))
        xmax = max(xmax,x)
        xmin = min(xmin,x)
        ymax = max(ymax,y)
        ymin = min(ymin,y)
        points.append((x,y))
    rect = True
    for point in points:
        x,y= point[0],point[1]
        if (x == xmin or x == xmax or y==ymin or y ==ymax ):
            continue
        else :
            rect = False
            break
    if rect:
        print( "YES")
    else:
        print ("NO")