Identify whether each of the following is best described as a fixed, variable, or mixed cost with respect to product units. Peanuts used in making trail mix. 2. Maintenance of factory machinery. 3. Rubber used in making tennis balls. Milk used in making ice cream. Electricity used in factory building. 6. Wages of an assembly-line worker paid on the basis of acceptable units produced. 7. Cameras used in making smartphones