Let $C=f(n)$ represent the total cost (in dollars) for a carpenter when she builds $n$ wooden chairs.

(a) If the carpenter currently builds $k$ chairs per week, what do the following expressions represent? Pick one (if any) of the statements in each pull-down menu which best explains its significance.
(i) $f(k+10)$ ? The cost of building 10 chairs less each week. The number of chairs you can build per week if total cost is increased by 10 dollars. The cost of building 10 more chairs per week. A decrease in weekly cost by 10 dollars. An increase in weekly cost by 10 dollars. The weekly cost if the cost per chair increases by 10 dollars. None of the above .
(ii) $f(k) + 10$ ? The cost of building 10 chairs less each week. The number of chairs you can build per week if total cost is increased by 10 dollars. The cost of building 10 more chairs per week. A decrease in weekly cost by 10 dollars. An increase in weekly cost by 10 dollars. The weekly cost if the cost per chair increases by 10 dollars. None of the above .
(iii) $f(2k)$ ? The cost of building half as many chairs per week. The number of chairs you can build in one week if the weekly cost is doubled. The cost of building two more chairs per week. The weekly cost if the cost per chair is doubled. The cost of building twice as many chairs per week. Double the weekly cost of building k chairs. None of the above .
(iv) $2f(k)$ ? The cost of building half as many chairs per week. The number of chairs you can build in one week if the weekly cost is doubled. The cost of building two more chairs per week. The weekly cost if the cost per chair is doubled. The cost of building twice as many chairs per week. Double the weekly cost of building k chairs. None of the above .

b) If the carpenter sells her chairs at 85% above cost, plus an additional 6% sales tax on the sale price, write an expression for her gross income (including sales tax) each week.
Gross Income =