Lele bought 4 identical pencils and a pencil case, and spent a total of 15.3 yuan. It is known that the unit price of a pencil is 1.2 yuan/piece, what is the unit price of this pencil case?
乐乐买了4支一样的铅笔和一个笔盒，共花了15.3元．已知铅笔的单价是1.2元/支，这个笔盒的单价是多少元个/个？
<gadget id="calculator">1.2 * 4</gadget>
<output>4.8</output>

<gadget id="calculator">15.3 - 4.8</gadget>
<output>10.5</output>

<result>10.5</result>