Jill, an economics student, has already spent 5 hours cleaning her room. In deciding whether or not to continue cleaning for another hour, she applies the economic principle of

Decreasing the reserve requirement ratio is

A) a contractionary policy because it lowers the amount of total reserves in the banking system. B) a contractionary policy because it lowers the amount of excess reserves in the banking system. C) an expansionary policy because it raises the amount of excess reserves in the banking system. D) an expansionary policy because it raises the amount of required reserves in the banking system.

DeShawn's Detailing is a service that details cars at the customers' homes or places of work. DeShawn's cost for a basic detailing package is $40, and he charges $75 for this service

For a total price of $90, DeShawn will also detail the car's engine, a service that adds an additional $20 to the total cost of the package. Should DeShawn continue to offer the engine detailing service? A) yes, but only if he raises the price of the basic detailing package B) No, his marginal benefit is less than his marginal cost. C) Yes, he still makes a profit by selling the engine detailing service with the basic detailing package. D) More information is needed for DeShawn to make this decision.