Select the Correct Answer: for Each Question

Multiple Choice

Select the correct Answer: for each question.
-The height of a hill (in feet) is given by where x is the distance (in miles) east and y is the distance (in miles) north of your cabin.If you are at a point on the hill 1 mile north and 1 mile east of your cabin, what is the rate of change of the height of the hill (a) in a northerly direction and (b) in an easterly direction?

A) (a) 570 ft/mi, (b) 690 ft/mi
B) (a) -570 ft/mi, (b) 690 ft/mi
C) (a) 690 ft/mi, (b) 570 ft/mi
D) (a) 690 ft/mi, (b) -570 ft/mi