The formula and calculation for getting simple interest is A = P (1 + rt). A stands for the answer which is the final investment. P is the principal amount of investment that needs to be provided at an interest rate (r) per time periods (t).
I believe the answer is: that will increase their well-being.
during the process, people would weight in the magnitude of benefit that they would obtain from doing a certain action compared to the expense and opportunities they need to sacrifice to obtain it. If the benefit is larger than the sacrifice, then people would see their action to be rational or purposeful
