The annual demand for an item is $2,000$ units. The cost to process an order is $$75,$ and the annual

inventory holding cost is $20\%$ of item cost.

$($a$)$ What is the optimal order quantity, given the following price breaks for purchasing the item?

$($b$)$ What price should the firm pay per unit?

$($c$)$ What is the total annual cost at the optimal behavior, including purchasing cost?