I just need an explanation of what "general factory overhead, which is allocated on the basis of the direct labour hours" means. I do not understand what they mean by on the "basis of direct hours". What does that imply for our calculations?

The Make or Buy Decision The special equipment used to manufacture part 4A has no resale value. The total amount of general factory overhead, which is allocated on the basis of direct labour hours, would be unaffected by this decision. The $30 unit product cost is based on 20,000 parts produced each year. An outside supplier has offered to provide the 20,000 parts at a cost of $25 per part. Should we accept the supplier's offer? 32