You are trying to plan for retirement in 20 years by depositing $10,000 every 6 months in your retirement savings account for the next 25 years, until retirement. Assume that the account returns 5% annual interest compounded semiannually, how much do you have at the end of 25 years?

I'm getting both $974,843.49 and

($845,794.01)

Can you please explain using excel