solve in excel woth steps with the equations you used

A company A buys products from company B. The company B proposed discounts: B - $50 per product on orders of 1 to 99 products - $49 per product on orders of 100 or more products. The ordering cost is $64 per order. The annual holding cost is 20 percent of the per unit purchase price. The annual demand is 500 products. What is the best purchase quantity