Selected Answer
Your calculation is correct. The result means that you would have to put $24,805 on the table today, wait for 25 years, and come back to collect $84,000. The result is negative because you have to pay less than the full amount. Put differently, $84000 +(-24805) = [expected interest].
Prove your calculation like this. Make the following entries in a blank worksheet.
[C1] =24805
[A2] =A1+1
[B2] =C1
[C2] =B2*1.05
Copy A2:C2 down to row 26. In column C you will see how your initial investment increases by 5% each year until it reached $83,998.53 after 25 years (column A). I presume that MSÂ won't make good your shortfall of $1.47. Instead, they are likely to be able to explain how this has to do with the difference between 365.25 actual days in a year and 365 days presumed by their formula. (Not good enough for me, lol: But who wants to argue with MS?)