use the following example and make amendments in it and add the asked functions in it using C++.

#include #include void addItem(int d); //prototypes void display(); struct Node{ int data; Node* next; }; Node *first=NULL,*last=NULL; //global pointer variables int main(){ addItem(2); addItem(84); addItem(6); display(); getch(); return 0; } void addItem(int n){ Node* ptrNew = new Node; ptrNew->data = n; ptrNew->next = NULL; if (first==NULL){ first = ptrNew; last = ptrNew; } else{ last->next = ptrNew; last = ptrNew; } } void display(){ Node* ptrCur = first; while(ptrCur!=NULL){ cout<data<next; } } Exercises: 1. Write a function to insert a new node at front of linked list. (at head) 2. Write a function to insert a new node after a node having certain value in a pointer based list. 3. Write a function to search maximum value from a pointer based linked list. 4. Write a function to delete node at head.