In this task, you need to answer the given multiple-choice question on the physics. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Example Input: Problem: the length of the bridge , which a train 130 meters long and travelling at 45 km / hr can cross in 30 seconds , is ? 
Options: a ) 288 , b ) 266 , c ) 245 , d ) 277 , e ) 211
Example Output: c

Example Input: Problem: the speed of a boat in still water in 42 km / hr and the rate of current is 6 km / hr . the distance travelled downstream in 44 minutes is : 
Options: a ) 86.6 km , b ) 46.6 km , c ) 35.2 km , d ) 35.6 km , e ) 26.6 km
Example Output: c

Example Input: Problem: in what time will two trains cross each other completely , which are running on the same parallel lines in opposite directions , each train running with a speed of 90 kmph being 160 m and 140 m in length respectively ? 
Options: a ) 5.6 sec , b ) 6.2 sec , c ) 6.0 sec , d ) 7.2 sec , e ) 6.8 sec
Example Output:
c