When the high-low method is used to estimate a cost function, the variable cost per unit is found by a. performing regression analysis on the associated cost and cost driver database. b. subtracting the fixed cost per unit from the total cost per unit based on either the highest or lowest observation of the cost driver. c. dividing the difference between the highest and lowest observations of the cost driver by the difference between costs associated with the highest and lowest observations of the cost driver. d. dividing the difference between costs associated with the highest and lowest observations of the cost driver by the difference between the highest and lowest observations of the cost driver.