Incorrect Question 6 A basic assumption of activity-based costing (ABC) is that: ' a) All manufacturing costs vary directly with units of production. b) Products or services require overhead activities and activities should be assigned to those products and services based on the quantity of those activities they consume. c) Only costs that respond to unit-level drivers are product costs. d) Only variable costs are included in activity cost pools. e) All products should be assigned an equal amount of overhead costs