The assumption that the velocity of money and the quantity being produced is constant is held by the:

A market

a. is often a physical place b. facilitates exchanges between buyers and sellers c. typically involves monetary transactions d. might not have well-defined geographical limits e. all of the above

If the production possibilities curve is a straight line,

a. opportunity costs rise as output of either commodity is expanded. b. resources are not equally productive in the production of both goods. c. opportunity costs are negative. d. resources can be moved from the production of one good to production of others with no loss of productivity.