One day at 8 o'clock in the morning, A starts from point A, while B sets off from point B to chase A, and ends up catching up at a distance of 9 kilometers from point B. If B doubles the speed, but A's speed remains the same, or B If you start 40 minutes earlier, you will catch up 2 kilometers away from B. What is the distance in miles between A and B?
某天早上8点甲从A地出发，同时乙从B地出发追甲，结果在距离B地9千米的地方追上，如果乙把速度提高一倍，而甲的速度不变，或者乙提前40分钟出发，那么将在距离B地2千米处追上．请问，A、B两地相距多少千米？
<gadget id="calculator">6 / 7</gadget>
<output>6/7 = around 0.857143</output>

<gadget id="calculator">(6/7) * 4.2</gadget>
<output>3.6</output>

<result>3.6</result>