Which statement about net cash flow is true?

a$.$ The firm's net cash flow is often called "the bottom line" since it is the lowest entry on the income statement.

b$.$ Depreciation reduces a firm's asset balance, so an increase in depreciation would normally lead to a decrease in the firm's net cash flow.

c$.$ Net Cash Flow $=$ Net Income $-$ Depreciation and Amortization Charges.

d$.$ Net Cash Flow $=$ Net Income $+$ Noncash Charges $-$ Noncash Revenues.