4. (30 points) Please write a stored function named fHW2 4 XXXX based on the Guest table. Your program should take one argument city and it should meet the following 3 test cases. 4A. 10 points) If the given city is in the 4B. (10 points) If the given city is empty Guest table, please return text with names for all or NULL, please display "Please input a valid city." guests whose address includes the given city. mysql select HW2 4 xxxx as output; mysql> select flw2 4 xxxx(London') as output mysql select fHW2 4 xxxx as output (NULL I output l output l Please input a valid city. I I John Kay, Mike Ritchie l I (10 points) If the given city is not in the Guest table, please display "No result found 4C. mysql select fHW2 4 xxxx ('Union') as output; I output I No result found