Scenario: Jim and Jane Are the Only Residents of an Apartment

Multiple Choice

Scenario: Jim and Jane are the only residents of an apartment building. The figures below show their demand curves for security guards (in hours of duty per day) who staff the entrance to the apartment. To answer some of the questions below, it will be useful to find the equations of the two lines in the figure.

-Refer to the figure above.If the market supply of guards' time is as in the figure below,what is the optimal number of guard's time for Jim and Jane?

A) 18 hours
B) 12 hours
C) 9 hours
D) 4 hours