2. The number of ways you can choose r things from a set of n, ignoring the order in which they are chosen, is () = n!/(r!(n - r)!). Let x be the first element of the set of n things. We can partition the collection of possible size r subsets into those that contain x and those that don't: there must be (?_?) subsets of the first type and (" ) subsets of the second type. Thus Text n n n + Using this and the fact that (2) = (6) = 1, write a function to calculate (2 ) . [Hint: develop a recursive function. In other words, you use the function within itself]