Question

Mark Zuckerberg invested $300 million in a savings account. If Mark makes no other deposits into this account, determine the amount in the savings account after 25 months if the interest rate is 2%.

Answer 1

That's a key question!

Let's assume that this is simple interest and that compounding is not part of the picture.  (This would not be typical of Mark Zuckerberg, by the way).

Then i = ($300 million ) (0.02)(25/12 year) =  $12.5 million, and
the total amount old Mark would then have, after 25 months would be
$312.5 million.