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'.

[Q]: Problem: if 21 lines are drawn in a plane such that no two of them are parallel and no three are concurrent , then in how many points do they intersect ?
Options: a ) 150 , b ) 170 , c ) 190 , d ) 210 , e ) 230
[A]: d

[Q]: Problem: two trains of equal length , running with the speeds of 60 and 40 kmph , take 55 seconds to cross each other while they are running in the same direction . what time will they take to cross each other if they are running in opposite directions ?
Options: a ) 10 sec , b ) 16 sec , c ) 13 sec , d ) 67 sec , e ) 11 sec
[A]: e

[Q]: Problem: find the distance covered by a man walking for 72 min at a speed of 10 km / hr ?
Options: a ) 12 km , b ) 3 km , c ) 4 km , d ) 5 km , e ) 6 km
[A]:
a