a$.$ Which of the following statements is FALSE?

A$.$ Incremental earnings are the amount by which the firm's earnings are expected to change as a result of the investment decision.

B$.$ The average cost of production will generally not change over time.

C$.$ Project externalities in a firm are direct effects of the project that may increase or decrease the profits of other business activities of the firm.

D$.$ Overhead expenses are associated with activities that are not directly attributable to a single project but are usually considered in free cash flow calculations.