HELP! I have no idea how to make the varying rate and terms table, I keep getting different numbers :((

The management at B-Fit would like to see a table that shows the Value of the Contribution for years of service varying 15 to 30 in increments of 3 years, and interest rates varying from 5% to 7% in increments of .5\%. Prepare the table. Since the Worksheet will be used for testing other values, you want to ensure that certain cell contents are not accidentally replaced. Protect the worksheet so that changes could be made only to entered data i.e. Annual Salary, Years of Service, Contributions (Percent), and Interest Rate. Users should not be able to change the contents of any other cells