Final answer:
Broker A should inform the seller and discuss with Broker B to clarify the situation.
Step-by-step explanation:
In these circumstances, Broker A should inform the seller about Broker B's arrangement of a sale of similar acreage at a considerably higher price to the same buyer.
Broker A has a fiduciary duty to act in the best interest of the seller and should disclose any information that might affect the seller's decision. By informing the seller, the seller can decide whether to proceed with the current transaction or explore other options.
Furthermore, Broker A should also consider discussing the situation with Broker B to clarify the details and determine if there was any unethical conduct involved.