What concept does economics primarily deal with?

In the long run the market supply

a. must always be horizontal. b. could be upward sloping if the cost of production falls as new firms enter the market. c. could be upward sloping if the cost of production rises as new firms enter the market. d. could be upward sloping if technological improvements lower the cost of producing in the market.

During 2016, Tony's assets equal $300,000 and his net worth is $50,000. Tony's liabilities are

A. $50,000. B. $150,000. C. $200,000. D. $250,000.