Which of the following statements regarding fixed and variable costs are true? Assume all costs are within the relevant range.

A. Total fixed costs increase with an increase in production, but unit fixed costs decrease with an increase in production.

B. Both total variable costs and unit variable costs remain constant with a decrease in production.

C. Unit variable costs decrease with an increase in production, but total variable costs increase with an increase in production.

D. Unit variable costs remain constant with a decrease in production, but total variable costs decrease with a decrease in production.

E. Both total fixed costs and unit fixed costs remain constant with an increase in production. F. Total fixed costs remain constant with an increase in production, but unit fixed costs decrease with an increase in production.