Which term best defines the high-low method Select one: O a. allows differentiation between fixed and variable costs when dealing with mixed costs. # O b. calculates variable costs per unit by dividing the difference in the high and low activity levels by the high and low costs O c. assumes that the fixed portion of the mixed cost is the lowest monthly cost incurred during the period under consideration. O d. combines the fixed and variable portions of a cost to determine the total cost