Answer: The company must rebuild the units.
Explanation: We must compare the benefits obtained by selling the defective units with the benefits obtained by selling the reconstructed units.
If we sell the defective units: 600 units × $2 = $1200
Versus
If we sell the rebuilt units: 600 units x ($5 - $0.60 [Materials] - $1 [Labor] - $0.80 [Overhead]) =
= 600 x ($2,60) = $1560.
Then it is convenient to rebuild the defective units to obtain a greater benefit.