I am pretty sure that the answer is the amount of taxes contributed by the employer plus the gross pay. Like I said, pretty sure, but 100% sure... I have doubts. Please help.

It does not include the gross pay. That's salary expense. It's the tax ONLY contributed by the employer. That is, it has nothing whatsoever to do with the pay to the employees at all, their gross, their deductions, nothing, because that's salaries and wages from the employer prospective.