The school is going to distribute pens to 15 classes, 144 pens per class, and 40 pens for teachers. How many pens should the school buy back?
学校准备发钢笔，发给15个班，每班144支，还要40支给老师用，学校应买回多少支钢笔？
<gadget id="calculator">144 * 15</gadget>
<output>2_160</output>

<gadget id="calculator">2_160 + 40</gadget>
<output>2_200</output>

<result>2_200</result>