A tradesman gives 4% discount on the marked price and gives 1 article free for buying every 15 articles and thus gains 35%. The marked price is increased above the cost price by

Pooja takes 3 times as much as time than Charu and twice as much time as Bano to do a work. If all three work together, she can finish the work in 2 hours. How long will it take Bano to do the whole work alone?