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 Q]: Problem: a and b runs around a circular track . a beats b by one round or 10 minutes . in this race , they had completed 4 rounds . if the race was only of one round , find the a ' s time over the course : 
Options: ['a ) 8.5 min', 'b ) 7.5 min', 'c ) 1.5 min', 'd ) 9.5 min', 'e ) 4.5 min']
[EX A]: b

[EX Q]: Problem: if 42 men do a work in 25 days , in how many days will 50 men do it ? 
Options: a ) 23 , b ) 22 , c ) 19 , d ) 20 , e ) 21
[EX A]: e

[EX Q]: Problem: a can complete a project in 20 days and b can complete the same project in 40 days . if a and b start working on the project together and a quits 10 days before the project is completed , in how many days will the project be completed ? 
Options: a ) 18 days , b ) 20 days , c ) 26.67 days , d ) 16 days , e ) 12 days
[EX A]:
b