Suppose you are climbing a hill whose shape is given by the equation z = 1,200 0.005x20.01y², where x, y, and z are measured in meters, and you are standing at a point with coordinates (160, 160, 816). The positive x-axis points east and the positive y-axis points north.
If you walk due south, will you start to ascend or descend?
a. ascend
b. descend

At what rate (in vertical meters per horizontal meter)?
___ vertical meters per horizontal meter