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'.

Ex Input:
Problem: a train 280 m long , running with a speed of 72 km / hr will pass a tree in
Options: a ) 14 sec , b ) 15 sec , c ) 16 sec , d ) 20 sec , e ) none

Ex Output:
a

Ex Input:
Problem: it takes joey the postman 1 hours to run a 7 mile long route every day . he delivers packages and then returns to the post office along the same path . if the average speed of the round trip is 8 mile / hour , what is the speed with which joey returns ?
Options: a ) 11 , b ) 12 , c ) 13 , d ) 8 , e ) 15

Ex Output:
d

Ex Input:
Problem: a man drives at a speed of 40 miles / hr . his wife left 30 mins . late with 50 miles / hr speed . when will they meet ?
Options: a ) 1 hours , b ) 2 hours , c ) 3 hours , d ) 4 hours , e ) 5 hours

Ex Output:
b