On a map with a scale of 1:4000000, the length of the railway line between A and B is measured to be 20 cm. How many kilometers are the actual length of the two subway tracks?
在比例尺是1：4000000的地图上，量得甲、乙两地的铁路线长为20厘米．两地铁轨实际长多少公里？
<result>800</result>