Both demand and surplus functions are linear. Demand function is as following : $Qd = 400 - 10P$. Equilibrium quantity is 200 units. Find the consumer gain
I tried to solve it this way: First I found P : $$Qd = 400 - 10P$$ $$10P=400$$ $$P=40$$ Then we have a formula : $$CG = 1/2(B*H)$$ As I have equilibrium 200 then my B is $$400/2=200$$ my H is $$40/2=20$$ So $CG= 1/2(20*400)=2000$ But I`m not sure about this answer, could you answer is it correct and if not where am I wrong.