2. The region R is a rectangle with vertices A (a, 10-a), B (0, 10-a), C (a, 0), and D (0, 0), where 0 < a < 1.
A.Write an expression that gives the area of the rectangle as a function of a.
B.The area of the rectangle is maximized for some c between 0 and 1. Write the expression you would need to solve in order to find c. You don’t need to find c.
C.What is the rate of change of the area when a =1, if a is decreasing at a rate of da/dt = − 0.3 units / sec? You don’t need to simplify, of course. Use appropriate units.
D.Again, a is decreasing at the rate of da/dt = − 0.5 units / sec. At a = 0.6, is the area of the rectangle increasing or decreasing? How do you know? Use appropriate units in your answer.
I appreciate the help 
