Just need to know what to type into the TVM keys on the calculator. My answers are not making sense to me.

1. a. You want to have $20,000 set aside in 4 years. How much money would you need to have set aside today in order to achieve your financial goal assuming you can earn 8% on your investment?

1. b. You want to have $20,000 set aside in 4 years. How much money would you need to set aside annually in order to achieve your financial goal assuming you can earn 8% on your investment?

1. c. You want to have $20,000 set aside in 4 years. You have $2,000 now to start with. How much additional money would you need to set aside annually in order to achieve your financial goal assuming you can earn 8% on your investment?