In the Colluding Refiners problem on the 2004 exam, is it possible to show MR on the graph?
See the other posts on demand and marginal revenue.
Also on this problem, why is DWL $5 million rather than $10 million?
I think you are right, in that the calculation should be 1/2 * ($2.50-$1.50)* 20 million. ($1.50 is the point on the supply curve at 100 million gallons.)