5. [G1.12] The height of a certain hill (in feet) is given by h(x, y) = 10 2xy − 3x 3 − 4y 2 − 18x + 28y + 12
where y is the distance (in miles) north, x the distance east of South Hadley. (a) Where is the top of the hill located? (b) How high is the hill? (c) How steep is the slope (in feet per mile) at a point 1 mile pe steepest at that point