Selected costs related to Apple's iPhone are listed below. Classify each cost as either direct materials, direct labor, factory overhead, selling expenses, or general and administrative expenses. 1. Uniforms provided for each factory worker 2 Wages for retail store salesperson 3. Glue to hold iPhone cases together 4 Wages for employees who maintain assembly equipment 5 Wages for assembly workers 6 Battery component 7 Microphone component 8 Wages for factory equipment operators