"A customer places an order with a registered representative to sell 5,000,000 shares of ABC stock (NYSE listed) "at the market." The registered representative should:"

Contact the firm's large block trading desk.

Explanation:

The reason why the registered representative would contact the firm's large block trading desk is because the order is larger than what can be handled normally on the Newyork Stock Exchange (NYSE) floor. Where large order as in the above is to be sold on the stock exchange floor, such would normally be presented to the firm's large block trading desk who will now decide on how best to handle the order; hence not the duty of registered representative.

Based on past experience, the trade desk would likely hand over the order to one of ABC's stock brokers for execution because for example, Super Display Book - NYSE automated system, which is responsible for dealing NYSE listed issues, has certain limited orders they can take.

i would say iii (3) because in order to compare a price you have to use as a reference other near stores because it's its

hope i explained myself