Consider the Spreadsheet for Stone Age Surfboards Provided Below -If the Unit Profit on Graystone Surfboards Is Increased by This

Consider the spreadsheet for Stone Age Surfboards provided below. Use this data to answer the following question(s) , using the Standard Solver.
Stone Age Surfboards is a small manufacturer of two types of popular low-tide surfboards, the Graystone and the Lava models. The manufacturing process consists of two departments: fabrication and finishing. The fabrication department has 8 skilled workers, each of whom works
9.25 hours per day. The finishing department has 5 workers, each of whom works a 6-hour shift per day. Each pair of Graystone surfboards requires 2.5 labor hours in the fabrication department and 2 labor hours in finishing. The Lava model requires 4.2 labor-hours in fabrication and 3.6 labor-hours in finishing. The company operates 6 days a week. It makes a per unit profit of $40 on the Graystone model and $60 on the Lava model. The company anticipates selling at least twice as many Lava models as Graystone models. $\begin{array}{|c|c|c|c|c|}\hline & \text { A } & \text { B } & \text { C } & \text { D } \\\hline 1 & \text { Stone Age Surfboards } & & & \\\hline 2 & & & & \\\hline 3 & \text { Data } & & & \\\hline 4 & &&{\text { Product }} & \\\hline 5 & \text { Department } & \text { Graystone } & \text { Lava } & \text { Limitation (hours) } \\\hline 6 & \text { Fabrication } & 2.5 & 4.2 & 74 \\\hline 7 & \text { Finishing } & 2 & 3.6 & 30 \\\hline 8 & & & & \\\hline 9 & \text { Profit/Unit } & \$ 40.00 & \$ 60.00 & \\\hline 10 & & & \\\hline 11 & & & \\\hline 12 & \text { Model } & & \\\hline 13 & & \text { Graystone } & \text { Lava } \\\hline 14 & \text { QuantityProduced } & & & \text { Hours Used } \\\hline 15 & \text { Fabrication } & & & \\\hline 16 & \text { Finishing } & & & \\\hline 17 & & & & \\\hline 18 & & & & \text { Excess Lava } \\\hline 19 & \text { Market Mixture } & & & \\\hline 20 & & & & \\\hline 21 & & & & \text { Total Profit } \\\hline 22 & \text { ProfitContribution } & & & \\\hline\end{array}$
-If the unit profit on Graystone surfboards is increased by $10, what is the shadow price for the finishing hours used?

A) $ 18.48
B) $ 17.39
C) $ 15.42
D) $ 14.15