The passenger car and the borrowed car travel in opposite directions from the midpoint of A and B at the same time. After 4 hours, the bus arrives at A, and the rented car is still 50 kilometers away from B. The ratio of the speed of the rented car to the passenger car is 3:4. How many kilometers are there between A and B?
客车和贷车同时从甲乙两地的中点向相反方向行驶，4小时后客车达甲地，贷车离乙地还有50千米，已知贷车速度与客车的比为3：4，甲乙两地相距多少千米？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">(1/2) - (3/8)</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">50 / (1/8)</gadget>
<output>400</output>

<result>400</result>