I have a handful of questions like this. I need help with the formula please!

Payouts and Annuities, Part III: Reaching a Goal For this part of the project, you will be looking at how to plan to save up in order to reach desired payout annuity goal. For each part, consider whether you should round up to the cent or down to the cent. E. When Riley retires, they would like to be able to withdraw $1250 semimonthly (twice per month) from their retirement account, and do so for 15 years. Their retirement annuity has a 6% APR. 20. If they start saving 10 years before retirement, how much will Riley need to depoist semimonthly to reach their goal? $ How much will they deposit in total over the 10 years? $