Please explain B and C and show work

please explain B and C

Phillip Flamm's Computer Store in Texas sells a printer for $220. Demand is constant during the year, and annual demand is forecasted to be 480 units. Holding cost is $40 per unit per year, whereas the cost of ordering is $90 per order. Currently, the company is ordering 12 times per year (40 units each time). There are 250 working days per year, and the lead time is 12 days. a) Given the current policy of ordering 40 units at a time, the total of the annual ordering cost and the annual holding cost is $ 1880 (round your response to the nearest whole number). b) If the company used the absolute best inventory policy, the total of ordering and holding cost is $ 1,859 (round your response to the nearest whole number). c) The reorder point is 23 units (round your response to the nearest whole number)