A department of Alpha Co. incurred the following costs for the month of September. Variable costs, and the variable portion of mixed costs, are a function of the number of units of activity: Activity level in units 5,500 Variable costs $9,700 Fixed costs 31,000 Mixed costs 20,500 Total costs $61,200 During October the activity level was 8,500 units, and the total costs incurred were $71,500. (a) Calculate the variable costs, fixed costs, and mixed costs incurred during October. (Do not round your intermediate calculations. Occtober Variable cost $ Fixed cost $ Mixed cost $ (b) Use the high