Answer:
b) Cognitive dissonance
Step-by-step explanation:
Cognitive dissonance is a concept used in psychology to refer to the discomfort that one person experiences when the person has two or more contradictory beliefs or ideas.
In real life, cognitive dissonance is usually triggered when we face new evidence that comes in contradiction with what we already believed or thought. This situation creates discomfort and the human psyche will try to find a way to reduce it by solving the contradiction faced by these two situations.
In this case, Stephan was convinced he really got a good deal for such a good computer and only paid $1200 dollars but suddenly he was confronted by new evidence when he saw a similar computer online on sale for only $1000, this situation created discomfort so he is trying to reduce it by thinking he might not have gotten such a good deal. Therefore, he is experiencing cognitive dissonance.