2. Safe Shades produces two types of sunglasses; Tortoise one sells for $17 Black one sells for $21. The total revenue in thousands of dollars per year for the sale of x thousand glasses at $17 each and y thousand glasses at $21 each is given by R(x,y) =17x+21y. The company has determined that the cost per year equation for these sunglasses is given by C(x,y) =4):2 4)ty+2y2 11x+25y3- a. Find the Prot function. [5 points] b. Use calculus to nd the critical point of the prot function and show that this is a maximum [10 points] c. How many of the tortoise and the black sunglasses must be sold for maximum prot? [3]