Lisa will invest some money on July 3, her sixteenth birthday, at 4.5% per year, compunded monthly. How much should she invest if she wants to have $10,000 on the November 3 following her eighteenth birthday? I have found P= 10,000 i= 0.045/12= 0.00375 n= ? ( not sure how to get this) Thank you for the help 2. This formula should do the trick..$\displaystyle P = \frac{A}{\left(1 + \frac{r}{n}\right)^{nt}}\$