Chapter 4.3, Problem 78E

To determine

(a)

To show,

The critical numbers of $C$ occur at the numbers $t$ where $C\left(t\right)=f\left(t\right)+g\left(t\right).$

To determine

(b)

The length of time $T$ for $D\left(t\right)$ to equal the initial value of $V.$

To determine

(c)

The absolute minimum of $C$ on $(0, T].$

To determine

(d)

To sketch:

The graph for $C$ and $f+g$

And verify the result in part(a)