Activity-based costing:
a. is an accounting system that assigns a company's expenses to whichever activity in a company's value chain is responsible for creating the cost
b. involves using benchmarking techniques to develop cost estimates for the value chain activities of each major rival
c. is a powerful tool for identifying the different pieces of a company's value chain and classifying them as primary activities and support activities
d. involves determining which value chain activities represent variable costs and which represent fixed costs
e. is a tool for identifying the activities that cause a company's product to be strongly differentiated from the products of rivals