Answer:
a. cognitive dissonance.
Explanation:
Cognitive dissonance is the psychological concept that describes the discomfort a person feels when he is having conflicting beliefs ideas or values at the same time. People tend to seek consonance (agreement) between the what they expect and reality.
In this instance Steve Walker got the computer he wanted at $12,000, seeing a similar computer at $10,000 makes him have a doubts about his purchase (cognitive dissonance).