crystallization reactor question

(6) The equation that describes a crystallization reactor is: R (number of crystals/minute) = a D-b D2 D = diameter of crystals, mm a and b = constants a- Determine the units of a and b Use values of a = 200 and b = 10 for the following questions: b- Rewrite the original equation in order to use D in inches and Rin number of crystals per second C- What are the units of the two new constants resulting from part c