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'.

Problem: a , b , k start from the same place and travel in the same direction at speeds of 30 km / hr , 40 km / hr , 50 km / hr respectively . b starts two hours after a . if b and k overtake a at the same instant , how many hours after a did k start ? 
Options: a ) 2.4 , b ) 3.2 , c ) 4.0 , d ) 4.8 , e ) 5.6
b

Problem: the edges of a cuboid are 4 cm , 4 cm and 6 cm . find the volume of the cuboid ? 
Options: a ) 90 , b ) 60 , c ) 96 , d ) 80 , e ) 72
c

Problem: if seven machines working at the same rate can do 3 / 4 of a job in 30 minutes , how many minutes would it take two machines working at the same rate to do 3 / 5 of the job ? 
Options: a ) 45 , b ) 60 , c ) 75 , d ) 84 , e ) 100

d