A community is a piece of land with an area of 0.8 hectares. Eight buildings are to be built. Each building covers an area of 500 square meters. The rest of the area is planned to be used for greening and building roads. How many square meters are the green spaces and roads?
某小区是一块面积是0.8公顷的土地，准备建成8幢楼房，每幢的占地面积是500平方米，其余部分准备用于绿化和兴建道路，绿地和道路的面积有多少平方米？
<gadget id="calculator">0.8 * 10_000</gadget>
<output>8_000</output>

<gadget id="calculator">500 * 8</gadget>
<output>4_000</output>

<gadget id="calculator">8_000 - 4_000</gadget>
<output>4_000</output>

<result>4_000</result>