20 marks] (Replace strings) Write the following function that replaces the occurrence of a substring old_substring with a new substring new substring in the string s. The function returns true if string s is changed, and otherwise, it returns false. bool replace_strings (string& s, const string& old_string, const string& new string) Write a test program that prompts the user to enter three strings, ie., s, old string, and new_string, and display the replaced string