Which of the following points are critical points for f(x,y)=x3+y3−3xyf(x, y) = x^3 + y^3 - 3xyf(x,y)=x3+y3−3xy?
(0,0)(0, 0)(0,0)
(1,1)(1, 1)(1,1)
(0,1)(0, 1)(0,1)
(1,0)(1, 0)(1,0)