Suppose this game is played sequentially. First, BHP chooses whether to try to sell a Small' or 'Large' quantity of iron ore on the spot market. Second, having observed this choice, the Chinese Steel Association decides whether to 'Block' or 'Not block' BHP from selling on the spot market. Finally, having observed the choice made by the Chinese Steel Association, BHP decides whether to ask for a 'Low' or 'High' price for long-term contract sales. c) What is the rollback equilibrium in the sequential version of the game