A warehouse sells 10,000 boxes of copy paper per year. It costs $150 to reorder from the factory. Each box costs $5 if the order quantity is less than 2000 units and costs $4.75 if the order quantity is more than 2000 units. The holding cost rate is 35% of the price. a) Find the optimal order quantity. b) For this optimal order quantity, calculate the inventory cost, the ordering cost, and the total cost per year