The theory of efficiency wages explains why? a. setting wages at the equilibrium level may increase unemployment.
b. it may be in the best interest of firms to offer wages that are above the equilibrium level.
c. the most rational way to pay workers is to pay them according to their skills.
d. it is the best for firms to set wages at the equilibrium level.

An allergy products superstore buys 6000 of their most popular model of air filters each year. the price of the air filters is $18. the cost of ordering and receiving shipments is $12 per order. accounting estimates annual carrying costs are 20% of the price. the supplier lead time is 2 days. the store operates 240 days per year. each order is received from the supplier in a single delivery. there are no quantity discounts. what is the store’s minimum total annual cost of placing orders & carrying inventory?