The demand function for a certain item is $$Q = 35\sqrt{32-p^2}.$$

$p$ represents the price of an item and $Q$ represents the number of items sold at that price.

(a) Evaluate the demand elasticity when $p= 3$.
$E(3)=$

(b) For what value of $p$ is the demand elasticity unitary?
$p=$

Here, "demand elasticity" is the absolute value of $\displaystyle \frac{\text{percent change in quantity}}{\text{percent change in price}}$ for an infinitesimal change in price, so $$E = \left| \lim_{\Delta p \to 0} \frac{ \Delta Q / Q}{\Delta p / p} \right| \ .$$