For this assignment, you will create an Object-Oriented C++ program that tests for palindromes. A palindrome is a string that reads the same backward as forward. For example, the words mom, dad, madam and radar are all palindromes. Write a class Pstring that is derived from the STL string class. The Pstring class adds a member function bool isPalindrome() that determines whether the string is a palindrome. Include a constructor that takes an STL string object as parameter and passes it to the string base class constructor. Test your class by having a main program that asks the user to enter a string. The program uses the string to initialize a Pstring object and then calls isPalindrome() to determine whether the string entered is a palindrome. Be sure to including comments throughout your code where appropriate. You may find it useful to use the subscript operator [] of the string class: if str is a string object and k is an integer, then str[k] returns the character at position k in the string.