The bus that travels from St. Louis to Chicago and back comes to St. Louis every 3 hours while the bus that travels from St. Louis to Springfield and back comes to St. Louis every 4 hours. If at 6:00 o'clock both bused arrived at St. Louis, at what time will they meet in St. Louis again?	Choose the correct choice from the following.
A) 16:00.
B) 18:00.
C) 20:00.
D) 22:00.
E) 24:00.
Time taken by bus to travel from St. Louis to Chicago and back comes to St. Louis = 3 hours   Time taken by bus to travel from St. Louis to Springfield and back comes to St. Louis = 4 hours   Time taken by both buses to meet again in St. Louis will be LCM of 3 and 4 = 12   If the buses start at 6:00 o'clock from St. Louis , they will meet again in St. Louis at 18:00 hours   Answer 18:00.
<result>B</result>
The bus that travels from St. Louis to Chicago and back comes to St. Louis every 3 hours while the bus that travels from St. Louis to Springfield and back comes to St. Louis every 4 hours. If at 6:00 o'clock both bused arrived at St. Louis, at what time will they meet in St. Louis again?