问题如下：
An analyst gathered the following information from a company’s 2010 financial statements (in $ millions):
In 2010, the company declared and paid cash dividends of $10 million and recorded depreciation expense in the amount of $25 million. The company considers dividends paid a financing activity. The company’s 2010 cash flow from operations (in $ millions) was closest to
选项：
A. 25.
B. 45.
C. 75.
解释：
B is correct.
All dollar amounts are in millions. Net income (NI) for 2010 is $35. This amount is the increase in retained earnings, $25, plus the dividends paid, $10. Depreciation of $25 is added back to net income, and the increases in accounts receivable, $5, and in inventory, $3, are subtracted from net income because they are uses of cash. The decrease in accounts payable is also a use of cash and, therefore, a subtraction from net income. Thus, cash flow from operations is $25 + $10 + $25 – $3- $5–$7 = $45.
解析：CFO的计算有直接法和间接法两种方法，根据题目给的AR、inventory和AP的条件可以确定应该是用间接法，间接法的CFO是从NI推出的，本题虽然没有给NI，但是给了RE和dividend，根据RE的BASE法则我们可以算出NI。期初RE+NI-dividend=期末RE，即120+NI-10=145，算出NI=35。再代入公式计算CFO=NI+dep –Δinv–ΔA/R+ΔA/P=35+25-（48-45）-（43-38）+（29-36）=45。
请问为什么要加会depreciation expense
