Mark, who recently won a lottery, tells Sean that he will split his lottery winn

Mark, who recently won a lottery, tells Sean that he will split his lottery winnings with him, if Sean can arrange an interview between Sean's boss and Mark. Sean talks to his boss and the meeting is arranged. But when Sean goes to collect half of Mark's lottery winnings, Mark refuses to pay. What is the act of consideration in this scenario?
A) Mark telling Sean he will split his lottery winnings with him
B) Sean arranging the interview
C) Mark going for the interview
D) Sean asking for half of the lottery winnings

This is for my business law class, anything will help