Uncle Yang surrounded a trapezoidal vegetable field with a fence near the wall. The total length of the fence is 24.6m, and the length of one side is 6.5m. What is the area of this vegetable field in square meters?
杨大伯在靠近墙处用篱笆围成一块梯形的菜地，篱笆全长24.6m，其中一边的长度为6.5m．这块菜地的面积是多少平方米．
<gadget id="calculator">24.6 - 6.5</gadget>
<output>18.1</output>

<gadget id="calculator">6.5 / 2</gadget>
<output>3.25</output>

<gadget id="calculator">18.1 * 3.25</gadget>
<output>58.825</output>

<result>58.825</result>