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: 8 persons can build a wall 140 m long in 42 days . in how many days can 30 persons complete a similar wall 100 m long ? 
Options: a ) 12 , b ) 10 , c ) 8 , d ) 6 , e ) 5
[EX A]: c

[EX Q]: Problem: some persons can do a piece of work in 8 days . two times the number of these people will do half of that work in ? 
Options: a ) 2 , b ) 4 , c ) 5 , d ) 6 , e ) 8
[EX A]: a

[EX Q]: Problem: a tyre has two punctures . the first puncture alone would have made the tyre flat in 9 minutes and the second alone would have done it in 6 minutes . if air leaks out at a constant rate , how long does it take both the punctures together to make it flat ? 
Options: a ) 315 min , b ) 325 min , c ) 335 min , d ) 345 min , e ) none of these
[EX A]:
c