Classify these items into the following categories: $(a)$ direct materials, $(b)$ direct labor, and $(c)$ manufacturing overhead.

Category

Salaries for product inspectors.

$2.$

Insurance $on$ factory machines.

$6.$

Property taxes $on$ the factory building.

Factory repairs.

Upholstery used $in$ manufacturing furniture.

Wages paid $to$ assembly$-$line workers.

Factory machinery depreciation.

Glue, nails, paint, and other small parts used $in$ production.

Factory supervisors' salaries.