Math Is Fun Forum

Suppose you are climbing a hill whole shape is given by the equation z=1000 - 0.005x^2 - 0.01y^2, where x, y and z are mesured in meters, and you are standing at a point with coordinates (60, 40, 966). The positive x-axis points east and the positive y-axis points north.
(a) If you walk due south, will you start to ascend or descend? At what rate?
(b) If you walk northwest, will you start to ascend or descend? At what rate?
(c) In which direction is the slope largest? What is the rate of ascent in that direction? At what angle above the horizontal does the path in that direction begin?

Please help me! Thanks.