Answer:
a. decrease by $58,800 per month
Explanation:
The computation is shown below;
<u>
Particulars Amount </u>
Contribution from product X $94,800 ($28 - $22) × 15,800 units
Less: Fixed cost -$108,000
Net loss avoided -$13,200
Non-avoidable fixed cost $72,000
The Total cost in case the product fall $58,800
Hence, the correct option is a.