Elm uses the high-low method of estimating costs. Elm had total costs of $214, 266 at its lowest level of activity, when 9, 600 units were sold. When, at its highest level of activity, sales equaled 15, 800 units, total costs were $394, 500. Elm would estimate variable cost per unit as $29.07 $22.32 $24.97 $23.97