The angles of elevation of the top of a building from the top and bottom of a tree are x and y respectively. If the height of the tree is h meter then, in meter, the height of the building is:
A and B can do a piece of work in 36 days. B and C can do the same work in 60 days. A and C can do the same work in 45 days. In how many days can A alone complete the same work?