The function C(x) = 15x + 4000 represents the cost to produce x number of items. Find the average cost function, then determine the number of items that should be produced so that the average cost is less than $65.

The manufacturer of a water bottle spends $5 to build each bottle and sells them for $10. The manufacturer also has fixed costs each month of $6500. (a) Find the cost function C when x bottles are manufactured. (b) Find the revenue function R when x bottles are sold. (c) Show the break-even point by graphing both the Revenue and Cost functions on the same grid. (d) Find the break-even point. Interpret what the break-even point means.