int foo(int N) { if (N <= 2) return 2; return foo(N-1) * (foo(N-1) + 3) - foo(N-1) + 4; } Use the function definition as is. There is no error. a) (6 points) Draw the tree that shows the function calls performed in order to compute foo(5) (the root will be foo(5) and it will have a child for each recursive call.) b) (6 points) Use that tree to compute the number of function calls (that is, the number of nodes in the tree). SHOW YOUR WORK. (Continue on the next page if needed) 5 c) (6 points) Is it possible to re-implement this function so that it has running time O(N)? If not, why not? If yes, write this O(N) implementation of foo in C.