A small business owner contributes $4,000 at the end of each quarter to a retirement account that earns 10% compounded quarterly.
(a) how long will it be until the account is worth at least $150,000?
(b)Suppose when the account reaches $150,000,the business owner increases the contribution to $4000 at the end of each quarter.What will the total value of the account be after 15 years? ​