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. use the spreadsheet below for stone age surfboards to answer the following question(s) using integer constraints on variables in the optimization models using the standard solver. what is the quantity of lava surfboards produced?