Answer:
Blake has already spent $5,600 in the production of the 280 defective units. It has to decide whether to sell them at $30 per unit or keep processing them at an additional cost of $10 per unit and then sell them at the regular price of $150 per unit.
If Blake decides to sell the defective units as they are it would get $8,400 in revenue, with a gross profit of $2,800 (= $8,400 - $5,600).
If Blake decides to further process the defective units and sell them, it would get $42,000 in revenue, with a gross profit of $33,600 (= $42,000 - $8,400).
The difference between further processing the defective units or selling them as they are is an incremental income of $30,800 (= $33,600 - $2,800)