Determine whether each statement is true or false

(d) The maximum value of Duf(a, y) is f= (x, y) + fy?(x, y). (e) Two different level curves of the graph of z = f(x, y) can intersect. (f) If lim (x, y) -+ (a, b) f(x, y) = L and f is defined at (a, b), then f(a, b) = L. (g) If f ( , y) = x+ y, the -1