Final answer:
Mason should write a check for $3,000 to cover what he owes.
Step-by-step explanation:
To determine the amount Mason owes, we need to use the information provided in the question. Since the question states that we should disregard the interest element, we can assume that there are no penalties or additional fees associated with the late filing. Therefore, Mason should write a check for $3,000 to cover what he owes.