There is a trapezoidal vegetable field, the upper base is 5.8 meters long, the lower base is 4.2 meters long, and the height is 2.5 meters. What is the area of this vegetable field?
有一块梯形的菜地，上底长5.8米，下底长4.2米，高2.5米．这块菜地的面积是多少？
<gadget id="calculator">5.8 + 4.2</gadget>
<output>10</output>

<gadget id="calculator">2.5 / 2</gadget>
<output>1.25</output>

<gadget id="calculator">10 * 1.25</gadget>
<output>12.5</output>

<result>12.5</result>