Program in cwrite a program that a daycare center manage their waiting list. the program stores requests for being added to the waiting list. each request was stored with the classroom, the child’s first name, last name, and contact phone number. the provided program waiting_list. c contains the struct request declaration, function prototypes, and the main function. complete the function definitions so it uses a dynamically allocated linked list to store the waiting list requests. complete the following functions: 1. append_to_list: a. ask the user to enter the classroom, child’s first name, and last name. b. check whether a request has already existed by classroom and the child’s first name and last name. if a request has the same classroom, first name and last name as an existing request in the list, the function should print a message about using the update function to update classroom and exit. c. if the request does not exist, ask the user to enter the contact phone number. d. allocate memory for the structure, store the data, and append it to (add to the end of) the linked list. e. if the list is empty, the function should return the pointer to the newly created linked list. otherwise, add the request to the end of the linked list and return the pointer to the linked list.2. update: update a request’s classroom. when a child is on the waiting list for a long period of time, he/she might need to be moved to the waiting list for another classroom. in this function, ask the user to enter the classroom, child’s first name, and last name. find the matching child, ask the user to enter the new classroom and update the classroom. if the child is not found, print a message.3. printlist: print the classroom, child’s first and last name, and contact phone number of all requests in the list.4. clearlist: when the user exists the program, all the memory allocated for the linked list should be deallocated. note: use read_line function included in the program for reading first name, last name, classroom, and phone number. waiting_list. c#include #include #include #include #define room_len 100#define name_len 30#define phone_len 15struct request{ char classroom[room_len]; char first[name_len+1]; char last[name_len+1]; char phone[phone_len+1]; ; struct request *next; }; struct request *append_to_list(struct request *list); void update(struct request *list); void printlist(struct request *list); void clearlist(struct request *list); int read_line(char str[], int n); / main: prompts the user to enter an operation code, ** then calls a function to perform the requested ** action. repeats until the user enters the ** command 'q'. prints an error message if the user ** enters an illegal code. /int main(void){char code; struct request *wait_list = null; printf("operation code: a for appending to the list, u for updating a book" ", p for printing the list; q for quit.\n"); for (; ; ) {printf("enter operation code: "); scanf(" %c", & code); while (getchar() ! = '\n') /* skips to end of line */; switch (code) {case 'a': wait_list = append_to_list(wait_list); break; case 'u': update(wait_list); break; case 'p': printlist(wait_list); break; case 'q': clearlist(wait_list); return 0; default: printf("illegal code\n"); }printf("\n"); }}struct request *append_to_list(struct request *list){//add your codereturn null; }void update(struct request *list){//add your code}void printlist(struct request *list){//add your code}void clearlist(struct request *list){//add your code}int read_line(char str[], int n){int ch, i = 0; while (isspace(ch = ; str[i++] = ch; while ((ch = ! = '\n') {if (i < n)str[i++] = ch; }str[i] = '\0'; return i; }