A break-even chart must be interpreted in the light of the limitations of its underlying assumptions

A break-even chart must be interpreted in the light of the limitations of its underlying assumptions … (From Cost Accounting: A Managerial Emphasis, by C.T. Horngren.) Required: (a) For any three of the underlying assumptions provided in answer to (a) above, give an example of circumstances in which that assumption is violated. Indicate the nature of the violation and the extent to which the break-even chart can be adapted to allow for this violation.