Math Help!

1) a)Explain why the graph of a simple interest investment where the interest is added yearly has been compared to a set of stairs.

b) What is an appropriate analogy for the graph of a compound interest investment?Why?

2) Suppose that you had $10 000 to invest. Compare the total amounts for simple investments and compound investments after 20 years for an annual interest rate of 9%. Assume the interest period is annual. Upload a copy of the spreadsheet to the dropbox or copy and paste in a screen shot, and identify the simple interest graph and the compound interest graph.