Answer:
The answer is the equity theory of motivation.
Step-by-step explanation:
The Theory of Equity, generally attributed to J. Stacy Adams, is one of several theories of motivation that emphasizes an individual's personal perception of reasonableness or relative fairness in his or her work relationship with the organization. In fact, the theory of equity assumes that motivation depends on the balance between what a person offers to the organization through the production system (its performance) and what it receives through the pay system (its compensation).
According to the authors of the theory, people are motivated whenever they expect to receive from the organization (whether in monetary form, public recognition, promotion, transfers, or otherwise) fair compensation for their efforts on behalf of the organization. The fairness of this compensation is assessed by people by comparing what other people receive whose contributions are similar. If compensation is unfair (less than compensation given to other people), people feel dissatisfied and tend to reduce their contributions.
This theory is what best explains Angela's situation.