According to social exchange theory, every interactions that people have will always be driven by cost-benefit analysis.
People tend to do a certain action if they feel that they can obtain some sort of positive value from it. (even when it's the act of giving something, the positive feeling that we obtain after giving can be considered as a ' benefit') .
From the case above, jennifer failed to contribute after she's about to run out of money. At that moment, she felt that the benefit (self-esteem) that she obtain from the donation is no longer outweigh the financial cost.
A progressive tax is a tax that imposes a lower tax rate on low-income earners compared to those with a higher income, making it based on the taxpayer's ability to pay. That means it takes a larger percentage from high-income earners than it does from low-income individuals.
