What is the size of the payments that must be deposited at the beginning of each 6-month period in an account that pays 8.6%, compounded semiannually, so that the account will have a future value of...

What is the size of the payments that must be deposited at the beginning of each 6-month period in an account that pays 8.6%, compounded semiannually, so that the account will have a future value of $170,000 at the end of 20 years? (Round your answer to the nearest cent.)
$_____