It takes 4 minutes for the master to produce 2 parts. It takes 7 minutes for the master to produce 1 piece and the apprentice to produce 1 piece. How many minutes will it take for the apprentice to produce 2 parts?
师傅生产2个零件要4分钟．师傅生产1个，徒弟生产1个共需要7分钟，如果徒弟生产2个零件需要多少分钟．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">7 - 2</gadget>
<output>5</output>

<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<result>10</result>