Read Chapter 3 of your Cornerstones of managerial Accounting 6th ed. and write a 1,000-word essay that covers the following topics:-Explain the meaning of discretionary and committed fixed costs (provide example).- Explain the formula:Total variable costs = Variable rate x Amount of output (provide example).-Explain the concept of mixed costs-Describe concept of step costsAll essays must include a comprehensive conclusion. Do not copy paste text. Make sure to include at least 5 external references with in-text citations. Use APA style.