The graph below shows a company's profit f(x), in dollars, depending on the price of pencils x, in dollars, being sold by the company:

part a: what do the x-intercepts and maximum value of the graph represent? what are the intervals where the function is increasing and decreasing, and what do they represent about the sale and profit? (6 points)

part b: what is an approximate average rate of change of the graph from x = 2 to x = 5, and what does this rate represent? (4 points)