The distance between A and B is 15 kilometers. A bus starts from B every 15 minutes to A at 8 o'clock every day, and the speed is 30 kilometers per hour. A person rides a bicycle from A to B at 8:20 at a speed of 15 km/h. How many buses from B can he see on the road?
甲、乙两地相距15千米，每天8点开始从乙地每隔15分钟开出一辆公共汽车到甲地去，车速是30千米/时．某人8点20分骑车从甲地到乙地去，速度是15千米/时．他在路上可以看到几辆从乙地开出的公共汽车？
<result>6</result>