Select all that apply Which of the following statements are true? When mixed costs are represented by a straight-line, the steeper the slope, the higher the variable cost per unit. The fixed portion of a mixed cost represents the cost incurred for th actual consumption of a service. The equation for a straight-line makes it easy to calculate the total mixed cost for any activity level outside the relevant range. A mixed cost has a minimum cost of having a service available and ready for use.