As I explain in my free lectures, the only difference ever between the marginal profit and the absorption profit is the change in inventory over the period multiplied by the fixed overheads per unit.
Here, the inventory is decreasing by 10,000 units over the period. Therefore the absorption profit is 10,000 x $6 = $60,000 lower than the marginal profit and so is $120,000.
I do suggest that you watch my free lectures. The lectures are a complete free course for Paper MA and cover everything needed to be able to pass the exam well.