Exercise reaction to a drug the strength of a human bodys

Question

Question: Refer to Exercise. Show that the rate of change in the reaction R with respect to the dosage D is maximal if D = k/2.

Exercise: REACTION TO A DRUG The strength of a human body's reaction R to a dosage D of a certain drug is given by

R = D²(k/2 - D/3)

Where k is a positive constant . Show that the maximum reaction is achieved if the dosage is k units.