Answer:
He should complete the additional work and sell the cabinet for $360.
Explanation:
This is because if he is to sell for $100 without completing the additional work, he will be making a loss of $80, having spent $180.
But on completion of the additional work, he would have spent a total of $380, therefore, if he sells the cabinet for $360, he will only be making a loss of $20.
Therefore, the better option is to complete the additional work and sell for $360.