A button is 0.5 yuan, a jacket has 5 buttons, and two sleeves each have 2 buttons. How much is the total cost of buttons for a jacket?
一个纽扣0.5元，一件上衣有5个纽扣，两个袖子各有2个纽扣，一件上衣的扣子共需多少元钱．
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">5 + 4</gadget>
<output>9</output>

<gadget id="calculator">9 * 0.5</gadget>
<output>4.5</output>

<result>4.5</result>