Plus it is very stylish and professional.

As another example, suppose that you just turned 25 and are planning for your retirement.
You hope to retire at the age of 60, and would like to be able to make
end-of-month withdrawals from your retirement account of $2,500 per month for
a 30-year period after that. If you plan on funding your retirement by making
monthly deposits between now and when you retire, with the first monthly deposit
occurring at the end of the coming month, how much must each deposit be if you
can earn 1 percent per month in your retirement account? (And, yes: we're going to
ignore taxes here.)....

In this problem, we have two annuities, one of deposits and one of withdrawals.
Since both involve monthly payments, we will need to have T expressed in terms of
months and r in terms of "per month." (Luckily, r is already given to us as a monthly
rate: we'll discuss how to handle converting it if it's not in the next chapter.)
The first step involves converting the annuity for the payments we do know, the
withdrawals into a lump sum. We have the choice of using either PVA or FVA
formulas to do so; but, if we remember where those two formulas will place the
lump sums, we can see that it will be better to use the PVA formula (because it will
place the value at the same point in time as the last deposit, perfectly positioned for
that value to be the FV of the deposit annuity). Solving for the PVA of the withdrawals
yields:

360 [T]
1% [r]
2,500 [C]
[CPT] [PVA] = 243,045.83