Cost-volume-profit analysis is a technique available to management to understand better the interrelationships of several factors that affect a firm's profit. As with many such techniques, the accountant oversimplifies the real world by making assumptions. Which of the following is not a major assumption underlying CVP analysis?

a.

All costs incurred by a firm can be separated into their fixed and variable components

b.

Operating efficiency and employee productivity are constant at all volume levels.

c.

The product selling price per unit is constant at all volume levels

d.

For multi-product situations, the sales mix can vary at all volume levels.