Step-by-step explanation:
We are given an investment of $15,000 invested for 13 years at an annual rate of 3.15%.
To calculate the Simple Interest on this investment, the formula given is;

Where the variables are;

We now have;


The value at the end of the investment period is now derived as;



To calculate value of this investment using the compound interest formula, we shall apply the formula which is;

Given the same variables as earlier, we simply substitute and solve as shown below;




We can round this to 2 decimal places and we'll have;

ANSWER:
Amount of the investment after 13 years will be $22,448.70