10- Implement the following function as a new function for the linked list toolkit. (Use the usual node definition with member variables called data and link. The data field is an int.)

int product(const node* head_ptr);

// Precondition: head_ptr is the head pointer of a linked list.

// The list might be empty or it might be non-empty.

// Postcondition: The return value is the product of all the data components

// of all the nodes. NOTE: If the list is empty, the function returns 1.