Tushar, Megha, Punam and Richa can complete a piece of work in 10 days, 12 days, 15 days and 18 days, respectively. In how many days will the work be completed if each of them work on alternate days starting with Megha on first day, Punam on second day, Richa on third day, Tushar on fourth day and then again Megha on fifth day and so on.