What is the difference between "profit" and "cash flow"?

a. There is no real difference between profit and cash flow.

b. A firm can maximize its cash flow only at the expense of its profit.

c. Profit refers to what is left after expenses have been subtracted from revenues, while cash flow refers to cash receipts and cash payments.

d. A firm can maximize its profit only at the expense of cash flow.

e. A firm cannot make a profit unless its cash flow is positive.