what does it mean to expand the contribution margin model 639250

What does it mean to state that the contribution margin model is more useful than the traditional model for determining the effect of changes in activity on operating income?
What does it mean to expand the contribution margin model?
What does it mean to state that the contribution model provides better support for decision making?
What does it mean that fixed expenses should not be unitized because they don’t behave that way?
What does it mean to state that contribution margin ratio is frequently a more useful measurement than contribution margin per unit?
What does it mean to break even?
What does it mean to state that a firm has a relatively high degree of operating leverage?