a$)**$ Graph: $f(x)=\{\begin{array}{ccc}x+1& or& x3\\ 2& \text{f}\text{o}\text{r}& x=3\end{array}$

b$),$ Find $\underset{x3}{lim}f(x)$

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c$)$ Find $f(3)$

d$)$ Is $f(x)$ continuous at $x=3?$

If an object has position $s(t)=t^4+t^2+3t$ with $s$ in feet and $t$ in minutes,

a$)$ Find the average velocity from $t=0$ to $t=2$ minutes.

b$)$ Find the velocity function $v(t).$

c$)$ Find the acceleration at time $t=3.$

$12.$ The monthly revenue for a manufacturer on the sale of $x$ units of a product is given by $R(x)=x^3+4x^2+160x.$ What is the marginal revenue when $70$ units are sold?

$13.$ The monthly cost for a manufacturer on the production of $x$ units of a product is given by $C(x)=-0\mathrm{.}035x^2+40x+25.$ What is the marginal cost when $600$ units are produced?

$14.$ In a certain memory experiment, a person is able to memorize $M$ words after $t$ minutes, where $M(t)=-0\mathrm{.}001t^3+0\mathrm{.}1t^2.$

$($a$)$ Find the number of words memorized after $10$ minutes.

$($b$)$ Find the rate of change of the number of words memorized after $10$ minutes.