Firm B's demand for a product is 10 units per month. Its supplier charges an ordering cost of $5 per order and $10 per unit with a 10% discount for orders of 15 units or highet. Firm B incurs a 30% annual holding cost. What is the optimal order quantity for Firm B f.e, the order quantity that minimizes the tota! purchasing, ordering, and holding cos? Muitiple Choice 20 22 21 15