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: a can finish a work in 12 days and b can do the same work in 15 days . b worked for 10 days and left the job . in how many days , a alone can finish the remaining work ?
Options: a ) 4 , b ) 5 1 / 2 , c ) 6 , d ) 8 , e ) none of these
[A]: a

[Q]: Problem: the speed of a car is 60 km in the first hour and 30 km in the second hour . what is the average speed of the car ?
Options: a ) 45 kmph , b ) 65 kmph , c ) 75 kmph , d ) 85 kmph , e ) 90 kmph
[A]: a

[Q]: Problem: a boy is traveling from his house to school at 10 km / hr and reached school 2 hours late . next day he traveled 20 km / hr and reached 1 hour early . then find the distance between house and school ?
Options: a ) 50 km , b ) 45 km , c ) 33 km , d ) 60 km , e ) 54 km
[A]:
d