Antonio lives in San Francisco and runs a business that sells boats. In an average year, he receives $722,000 from selling boats. Of this sales revenue, he must pay the manufacturer a wholesale cost of $422,000; he also pays wages and utility bills totaling $268,000. He owns his showroom; if he chooses to rent it out, he will receive $2,000 in rent per year. Assume that the value of this showroom does not depreciate over the year. Also, if Antonio does not operate this boat business, he can work as a paralegal, receive an annual salary of $21,000 with no additional monetary costs, and rent out his showroom at the $2,000 per year rate. No other costs are incurred in running this boat business. Identify each of Carlos's costs in the following table as either an implicit cost or an explicit cost of selling pianos.

a. The rental income Carlos could receive if he chose to rent out his showroom
b. The wages and utility bills that Carlos pays
c. The wholesale cost for the pianos that Carlos pays the manufacturer
d. The salary Carlos could earn if he worked as a paralegal