Final answer:
Mason can deduct $2,667 of the interest expense on the educational loan.
Step-by-step explanation:
Mason can deduct $2,667 of the interest expense on the educational loan. The maximum amount of interest expense that can be deducted on an educational loan is $2,500.
However, this limit is reduced if the taxpayer's modified AGI exceeds a certain threshold. For single taxpayers, the phase-out range starts at $70,000 and ends at $85,000. Mason's modified AGI of $90,000 falls within this phase-out range, so his deduction is reduced proportionally.