$[6\mathrm{.}67/10$ Points$]$

$$ LARAPCALC$102\mathrm{.}3\mathrm{.}031.$

Marginal Cost The cost $C($in dollars$)$ of producing $x$ units of a product is given by the following.

$c=3\mathrm{.}4\sqrt[\phantom{2}]{x}+400$

$($a$)$ Find the marginal cost $($in dollars per unit$)$ when $x=9.($Round your answer to two decimal places.$)$

$ $$ per unit

$($b$)$ Find the additional cost $($in dollars$)$ when the production increases from $9$ to $10$ units. $($Round your answer to two decimal places.$)$

$ $$

$($c$)$ Compare the results of parts $($a$)$ and $($b$).$

$$