问题详情

At 9:00 a. m. train T left the train station and two hours later train S left the same station on a parallel track. If train T averaged 60 kilometers per hour and train S averaged 75 kilometers per hour until S passed T, at what time did S pass T？
A．2:00 p.m.
B．5:00 p.m.
C．6:00 p.m.
D．7:00 p.m.
E．9:00 p.m.请帮忙给出正确答案和分析，谢谢！