3. Write a program that prompts the user to enter a sequence of capital and small letters as "ABcdEFgh" and store them in a doubly linked list and then do the following: a) Write a function convert that checks each letter case. If it is a small letter convert it into a capital letter, otherwise do nothing. b) Write function Order that orders the letters in an ascending order in the linked list. c) Store capital letters in stackl and small letters in stack2. d) Write function getHeight that prints the height of each stack and setHeight that checks if one stack has more elements than the other, then change its height by removing the top elements till both stacks become equal in height. [Note: implementation for the doubly Linked List is required]