The waterway between two docks A and B is 80 kilometers long. It takes Ship A 4 hours to go down the current and 10 hours to go upstream. If boat B takes 5 hours to travel downstream, what is the speed of boat B in still water?
A、B两个码头之间的水路长80千米，甲船顺流而下需要4小时，逆流而上需要10小时．如果乙船顺流而行需要5小时，那么乙船在静水中的速度是多少？
<gadget id="calculator">80 / 5</gadget>
<output>16</output>

<gadget id="calculator">80 / 4</gadget>
<output>20</output>

<gadget id="calculator">80 / 10</gadget>
<output>8</output>

<gadget id="calculator">20 - 8</gadget>
<output>12</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">16 - 6</gadget>
<output>10</output>

<result>10</result>