A road starts at town A and goes into the mountains. ?

Question

A road starts at town A and goes into the mountains. When you are x kilometers from along the road from A, the height above town A is h(x) meters.

(a) What does h(12) = 400 mean?

(b) What does h'(12) = -60 mean?

(c) If h(12) = 400 and h'(12) = -60 what, approximately, is the height of the road above A at a distance of 12.1 kilometers from A?