Xiaohong goes to the store to buy 2 pens and 4 notebooks. Each pen is 8 yuan, and each notebook is a yuan. So how much does Xiaohong have to pay in total?
小红到商店买2支钢笔和4本笔记本．每支钢笔8元，每本笔记本a元．则小红一共要付钱多少元．
<gadget id="calculator">16 + 4</gadget>
<output>20</output>

<result>20</result>