During the year, Casablanca Inc. increased its accounts receivable by $300, decreased its inventory by $180, increased its long-term debt by $300 and decreased its account payable by $160. How much did these three accounts affect the firm's cash flow from operating activities during the year? a. $40 source of cash. b. $20 use of cash. c. $20 source of cash. d. $280 use of cash. e. $280 source of cash.