Use the Following Information to Answer Questions $S M C = 200 - 15 Q + 0.8 Q ^ { 2 }$

Use the following information to answer Questions .
Radon Research Corporation (RRC) is one of 24 firms in Albuquerque testing homes for dangerous levels of radon gas. There is a standard test that all testing companies use. The manager of RRC wants to know the number of homes to test in 2015 in order to maximize the firm's profit. The manager forecasted a price of $160 for radon tests in 2015.
The firm's marginal cost was estimated as $S M C = 200 - 15 Q + 0.8 Q ^ { 2 }$ where Q is the number of tests performed each week. RRC's fixed cost will be $250 per week.
-How many radon tests per week should be undertaken?

A) 12.5
B) 15.5
C) 16.8
D) 17.3
E) 20