How would you do the following derivative problem?

nietzsche asked: Does anyone know how to do these problems? If you could show how to do it and what the answers would be, it would be greatly appreciated!! Thanks!
The quantity (in pounds) of a gourmet ground coffee that is sold by a coffee company at a price of p dollars per pound is Q [...]

How would you do this derivative problem?

nietzsche asked: Does anyone know how to do these problems? If you could show how to do it and what the answers would be, it would be greatly appreciated!! Thanks!
The quantity (in pounds) of a gourmet ground coffee that is sold by a coffee company at a price of p dollars per pound is [...]