How do you think that a team leader should react to the following two situations

How do you think that a team leader should react to the following two situations
How do you think that a team leader should react to the following two situations: a) A team member has made a significant mistake. b) Another member of the team has turned in an above-average performance. Analyze and discuss the differences and similarities in what you think the team leader's approach should be to other classmates' approaches in these situations?