Let $$\displaystyle{}\quad {f(x) = } \begin{cases} x^{3}+{\frac{729}{64}} & x \leq {\frac{9}{4}} \\ \frac{9x^{2}}{2} & x>{\frac{9}{4}} \end{cases}$$
(a) Is $f$ differentiable at $x={\frac{9}{4}}$ ? Yes No

(b) If $f$ is differentiable at $x={\frac{9}{4}}$ enter the value of $f'({\frac{9}{4}})$. If $f$ is NOT differentiable at $x={\frac{9}{4}}$ enter the value of $f({\frac{9}{4}})$ instead.

$f'({\frac{9}{4}})$ or $f({\frac{9}{4}})$ =