The school builds a new swimming pool with a length of 50 meters, a width of 15 meters, and a depth of 1.6 meters. A water level line should be drawn at a distance of 0.4 meters from the mouth of the pool. What is the length of the water level line in meters?
学校新建一个长为50米，宽为15米，深为1.6米的游泳池，要在距池口0.4米处画一条水位线，水位线的长度是多少米？
<gadget id="calculator">50 + 15</gadget>
<output>65</output>

<gadget id="calculator">65 * 2</gadget>
<output>130</output>

<result>130</result>