12-17 High-low method LO 6 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 4,500 Variable costs $ 8,100 Fixed costs 29,000 Mixed costs 24,160 Total costs $ 61,260 During October the activity level was 7,800 units, and the total costs incurred were $68,500. Required: a. Calculate the variable costs, fixed costs, and mixed costs incurred during October. October Variable cost Fixed cost Mixed cost