for t in range(int(input().strip())):
    x,y = [],[]
    for q in range(int(input().strip())):
        a,b = map(int,input().strip().split())
        x.append(a)
        y.append(b)
    a,b,c,d = max(x),max(y),min(x),min(y)
    f = 1
    for i in range(len(x)):
        m,n = x[i],y[i]
        if m < a and m > c and n < b and n > d:
            f = 0
            break
        elif m > a or m < c or n > b or n < d:
            f = 0
            break
    if f == 0:
        print('NO')
    else:
        print('YES')