How do I calculate the Present Value of a Deferred Annuity?

I am having a little trouble calculating the Present Value of a deferred Annuity. This is the question I have from my book:

What price will a finance company pay to a merchant for a conditional sale contract that requires 15 monthly payments of $231 beginning in six months? The finance company requires a rate of return of 18% compounded monthly.

How would I calculate this? The answer to the question is: $2861.16, but I keep getting a different answer.

Please help.

Thanks