Grandpa Li likes to raise pigeons. He uses a net to form an area 2 meters long and 3.42 meters wide to raise pigeons. It is known that the net costs 2.5 yuan per meter. How long does Grandpa Li want to buy back? How much will it cost?
李爷爷喜欢养鸽子，在天台用网围成一个长2米，宽3.42米的区域养鸽子，已知每米网要2.5元，李爷爷要买回多长的网？要花多少钱？
<gadget id="calculator">2 + 3.42</gadget>
<output>5.42</output>

<gadget id="calculator">5.42 * 2</gadget>
<output>10.84</output>

<gadget id="calculator">10.84 * 2.5</gadget>
<output>27.1</output>

<result>27.1</result>