A bookseller has 420 science stream books and 130 art stream books. He wants to stack them in such a way that each stack has the take same number and they take up the least area of the surface (a) What is the maximum number of science stream books that can be placed in e stack for this purpose? (b) which mathematical concept used to solve the problem? (c) If the bookseller makes a stack, then which kinds of quality are shown by the bookseller?