like for how much time the person can work, plzz dont send soln just help me understand the question, i am not getting it.
Plzz elaborate the question properly,,
@nmoudgil_be19 there is no limit for how much time a person can work.
simply saying you need to select a set of activities whose working time do not collapse with each other since a person can work only a single activity at a time.and you need to maximize size of this set of activities.
ok thanks 
okay happy to help.
if you got any problem let me know else mark this doubt as resolved.
Why have you reopened the doubt?