Can someone please help me with a Calculus problem?

Question

I'm not looking for someone to do my homework but I have this problem and I'm really confused and I don't know what to do to solve it:

The reaction of a body to a dose of medicine can often be represented by an equation of the form:

R= M^2(C/2-M/3)

where C is a positive constant and M is the amount of medicine absorbed in the blood. If the reaction is a change in blood pressure, R is measured in millimeters of mercury. If the reaction is a change in temperature, R is measured in degrees, and so on.

Find dR/dM. The derivative, as a function of M, is called the sensitivity of the body to medicine.

Please, any help would be greatly appreciated.

Answer 1

R = M^2(C/2-M/3)

If you meant: M^2*(C/2-M/3), you can distribute the parenthesis:
M^2*(C/2-M/3) = CM^2 / 2 - M^3/3
dR/dM = CM - M^2

Answer 2

dR/dM=M^2(-1/3)+(C/2-M/3)*2M
=(-1/3)M+2(C/2-M/3)*M