Continuous growth and decay

Lessons

1. On Aiden's 10-year-old birthday, he deposited $20 in a savings account that
   offered an interest rate of 4% compounded continuously. How much money
   will Aiden have in the account when he retires at the age of 60?
   
2. A radioactive substance decays continuously. If the half-life of the substance
   is 5 years, determine the rate of decay.