(a) We sometimes need to find how long it will take a sum of money (or anything else) to grow to some specified amount. (a) For example, if a company's sales are growing at a rate of 5.6% per year, approximately how long will it take sales to triple? Show your answer to 2 decimals (x.xx years)

(b) If you want an investment to double in 6 years, what interest rate must it earn? Show your answer to 2 decimals (x.xx%)