#### Answer

(a) $\frac{d}{dR}R=1$.
(b) $\frac{d}{dR}r=0$.
(c) $\frac{d}{dR}r^2R^3=3r^2R^2$.

#### Work Step by Step

(a) $\frac{d}{dR}R=1$.
(b) Since $ r $ is constant, we have $\frac{d}{dR}r=0$.
(c) Since $ r $ is constant, we have $\frac{d}{dR}r^2R^3=3r^2R^2
$.