One assumption of break$-$even analysis is that variable costs change linearly as production levels change. For Dell Computers, a company that develops, designs, and sells computers, this assumption would imply that:

a$.$

Outsourcing packaging would lead to increased costs associated with manufacturing products.

b$.$

Investing in new machinery would lead to higher costs for producing computers at Dell.

c$.$

The monthly rent paid by Dell remains constant throughout the analysis.

d$.$

Dell's overhead costs increase proportionately to the demand for computers.