1.12   The height of a certain hill (in feet) is given by

where y is the distance (in miles) north, x is the distance east of South Hadley.

1. Where is the top of the hill located?

2. How high is the hill?

3. How steep is the hill (in feet per mile) at a point 1 mile north and one mile east of South Hadley? In what direction is the slope steepest at that location?