3. Words frequency: Prompt the user for N words that the user wants to search for in the input string. Use a dynamic C++ string array allocated on the heap to store N words, and output the frequency of N given words in the input string. Example: User enters This is a test sentence, is this?, then 3 words, this, text, and test. The program outputs: this: 2 text: 0 test: 1 (Note: Case insensitive, meaning word and WoRD are the same; All numbers and special characters in the string are ignored, meaning wor32rd, wo]]]rd343.34, and word are the same)