Consider the following. y = x3 - 9x2 + 27x - 18 y 20 18 16 14 12 10 8 6 4 2 -2 5 (a) Estimate the coordinates of the relative maxima, relative minima, or horizontal points of inflection by observing the graph. (If an answer does not exist, enter DNE.) relative maxima (x, y) = relative minima ( x, V ) = horizontal points of inflection (x, y) = (b) Use y' = f'(x) to find the critical values. (Enter your answers as a comma-separated list.) X : (c) Find the critical points. (x, y) =