Beibei went to the bookstore to buy a notebook. He bought a notebook for 5.9 yuan, which was 0.6 yuan short, so he had to buy a notebook for 4.8 yuan. The remaining money just bought a ballpoint pen. How much is this ballpoint pen?
贝贝到书店买笔记本，买5.9元一本的，差0.6元，他只好买4.8元一本的，剩下的钱正好买了一支圆珠笔．这支圆珠笔多少钱？
<gadget id="calculator">5.9 - 0.6 - 4.8</gadget>
<output>0.5</output>

<result>0.5</result>