Use the Following General Linear Demand Relation $$Q _ { d } = 680 - 9 P + 0.006 M - 4 P _ { R }$$

Multiple Choice

Use the following general linear demand relation: $$Q _ { d } = 680 - 9 P + 0.006 M - 4 P _ { R }$$ where M is income and $$P _ { R }$$ is the price of a related good,R.If M = $15,000 and $P _ { R }$ = $20 and the supply function is $Q _ { 5 } = 30 + 3 p$ ,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.