Use the Following General Linear Demand Relation: Where P

Use the following general linear demand relation: where P is the price of good X,M is income,and is the price of a related good,R.Income is $80,000,and the price of the related good is $40.Also let consumers' tastes change so that consumers now demand 100 more units at each price.When the price of the good is $50,how many units of the good are demanded?

A) 70
B) 200
C) 220
D) 100
E) none of the above