P.3 5. The figure shows the graph of
y= -kx² - 4x + m. It cuts the x-axis at two points A and B. Given that the graph passes through the points (4, -18) and (-2,30).
(a) Find the values k and m. (b) Hence, find the coordinates of A and B.
(c) C is a moving point on the above graph. When C is above the x-axis, find the maximum area of ABC.