Solve 4 programming tasks using C# or Javascript

I have 4 different programming tasks that need to be implemented using C# and to include extensive comments describing how the solution was reached. A sample task (not the actual one) is to write a function that produces a list of products based on what your friends are buying. You are given two functions: getFriendsListForUser(): This function returns a list of users who are friends of a given user. getPurchasesForUser(): This function returns a list of products that have been purchased by a given user. The function you are asked to write will create a list of all the products purchased by a given user’s friends, ranked by frequency - the most frequently purchased products should appear first. The list should exclude any products that the user has already purchased. First actual task is: Each node of a Binary Search Tree (BST) has an integer value and pointers to as many as two children. The children of a parent node are referred to as the left child and the right child. The value of left child is always less than the value of its parent node, and the value of right child is always greater than or equal to the value of its parent node. Function Description: Write a function called "isPresent" in the editor below. The function must return 1 if the value is present in the BST, or 0 if it's not. isPresent has the following parameter(s): root: reference to the root node of a singly-linked list of integers val: integer to search for Constraints: 1 ≤ total nodes ≤ 10 1 ≤ val ≤ 5 × 10 /* For your reference class Node { Node left, right; int data; Node(int newData) { left = right = null; data = newData; } } */ Who can get the answer to me the fastest?