A department of Delta Company incurred the following costs for the month of June. Variable costs, and the variable portion of mixed costs, are a function of the number of units of activity: Activity level in units Variable costs Fixed costs 3,500 $ 7,350 31,000 18,000 Mixed costs Total costs $ 56,350 During July, the activity level was 9,000 units, and the total costs incurred were $69,500. Required: a. Calculate the variable costs, fixed costs, and mixed costs incurred during July. b. Use the high-low method to calculate the cost formula for mixed cost. Complete this question by entering your answers in the tabs below. Required A Required B Use the high-low method to calculate the cost formula for mixed cost. Note: Do not round intermediate calculations and round your answers to 2 decimal places. Cost formula = per unit < Required A Required B >