The school library originally had 574 science and technology books, 353 of which were loaned out, and 237 were returned. How many science and technology books are there in the library now?
学校图书室原有科技书574本，借出353本，还回237本，现在图书室有多少本科技书？
<gadget id="calculator">574 - 353</gadget>
<output>221</output>

<gadget id="calculator">221 + 237</gadget>
<output>458</output>

<result>458</result>