Finance question that I can't get the answer of!!?

Compare two stocks. Both have earned 8% per year on average. However, stock A has oscillated between 6% and 10%. Stock B has oscillated between 3% and 13%. (For simplicity, say that they alternated.) If you had purchased $500 in each stock, how much would you have had 10 years later? can someone tell me the answer and explain how we got there?