What are the different methods to measure industry concentration?

The above figure shows the isoquants for producing steel. Increasing returns to scale are

A) present when producing less than 10,000 tons. B) present when producing less than 20,000 tons. C) present when producing less than 30,000 tons. D) never present.

Show Stoppers is a monopoly provider of ticket services for the concerts and sporting events and their current service charge is $10.00 . In order to attract one more customer, they have to lower their service charge to $9.50 . Show Stoppers' marginal revenue of this additional customer is: a. $9.50

b. greater than $9.50. c. less than $9.50. d. between $10.00 and $9.50.