Explain how mixed costs are related to both fixed and variable costs. A. Mixed costs have a fixed portion that is a cost per unit of cost driver activity. Mixed costs also have a variable portion that is usually a cost per time period. B. Mixed costs are the sum of the fixed and variable costs that are related to equipment costs. These mixed costs are a form of committed costs during the production phase. C. A mixed cost is the sum of fixed costs and the portion of variable costs that are related to salaries and wages. These mixed costs are discretionary costs that easily fluctuate and must therefore be kept separate during a production phase. D. A mixed cost has a fixed portion that is usually a cost per time period. A mixed cost also has a variable portion that is a cost per unit of cost driver activity.