Final answer:
Arthur offered to sell his house to Mike for $50,000. Even before Mike responded to the offer, Jack learnt of the offer and called up Arthur to accept the offer. Jack's action represents an interference or a mistaken acceptance attempt.
Step-by-step explanation:
The scenario described involves an offer of a house sale between Arthur and Mike. When Jack attempts to accept the offer made to Mike, he is engaging in an action that cannot be considered a valid acceptance in legal terms, since the offer was not directed at him.
This situation outlines important concepts in contract law regarding the communication and acceptance of offers. Jack's action is legally ineffective because an offer can only be accepted by the person to whom it is made. Thus, Jack's action represents a form of interference or an invalid attempt to accept an offer not extended to him, which might also be described as a mistaken acceptance attempt.