In: Economics
We have
P = 100 cents
MC = 20 cents
Q(current) = 1000
Now we know that at profit maximizing level 1/ed = (P – MC)/P
1/ed = (100 – 20)/100
This gives ed = 1.25 or -1.25
Now demand is Q = A – BP
1000 = A – B*100
And ed = slope of demand * P/Q which gives -1.25 = -B * 100/1000
This results in B = 12.5 and A = 2250
Demand function is Q = 2250 – 12.5P
DWL = 0.5*(monopoly price – competitive price)*(competitive quantity – monopoly quantity)
Here monopoly price is 100 cents, competitive price is 20 cents, monopoly quantity is 1000 and competitive quantity is 2250 – 12.5*20 = 2000
DWL = 0.5*(100 – 20)*(2000 – 1000)
= 40000 cents
= $400.
As far as the justification is concerned, note that the firm has patent which means it has invested huge amount initially in research and development. Patents do generate deadweight loss due to the creation of monopoly but they are necessary for encouraging firms to take up investment and continue innovate new drugs. In this manner, this deadweight loss is justified.