Use the Following General Linear Demand Relation to Answer Questions

Use the following general linear demand relation to answer questions 9 through 13:

where M is income and is the price of a related good, R.
-If M = $15,000 and

= $20 and the supply function is

, then, when the price of the good is $40,

A) there is equilibrium in the market.
B) there is a shortage of 180 units of the good.
C) there is a surplus of 180 units of the good.
D) there is a shortage of 80 units of the good.