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

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 scenario above.To construct the market (Jim and Jane) demand curve for security guards,you must add the two curves ________,since security guard's service is ________.

A) horizontally; a rival good and exclusive
B) horizontally; a rival good but non-exclusive
C) vertically; exclusive but non-rival
D) vertically; non-rival and non-exclusive