Final answer:
Dillon's depletion deduction for 2015 is $220,000.
Step-by-step explanation:
To determine Dillon's depletion deduction for 2015, we need to calculate the total amount of depletion for the units mined. First, calculate the depletion per unit by dividing the purchase price by the estimated recoverable units: $3,500,000 / 500,000 = $7 per unit. Next, calculate the depletion for the units mined by multiplying the depletion per unit by the number of units mined: $7 * 40,000 = $280,000. Finally, subtract the expenses incurred during 2015 from the depletion for the units mined to find Dillon's depletion deduction: $280,000 - $500,000 = $220,000.