Cooper Section $8\mathrm{.}2\backslash$#$9$

After $\backslash ($ t $\backslash )$ years I have $\backslash ($ f$($t$)\backslash )$ thousand dollars in the bank.

a$.$ What are the units of $\backslash ($ f$^\{\backslash$prime$\}($t$)\backslash )?$

A$.$ Dollars per year

B$.$ Years

C$.$ Thousands of dollars per year.

D$.$ Thousands of dollars

E$.$ Years per thousand dollars

F$.$ Dollars

b$.$ What is the practical meaning of $\backslash ($ f$^\{\backslash$prime$\}(7)=0\mathrm{.}3\backslash )?$

A$.$ My account is increasing at a rate of $30$ cents per year at the start of year $7.$

B$.$ My account will increase by $300$ dollars during the $7$th year.

C$.$ My account is increasing at a rate of $7000$ dollars a year in April of the first year.

D$.$ My account is increasing at a rate of $300$ dollars per year at the start of year $7.$