3. (5 points) You are given a binary search tree with each node having a left and a right child. If there are no children in the left or right branch, the respective pointers are NULL. Complete the lookup C function to look up a key in the binary search tree. The function returns 1 if the key is found and returns 0 if the key is not found. /*structure for the binary search tree/ struct nodef int value; struct node* left; struct node* right; 1 /* initially curr points to the root of the tree/ int lookup (struct node* root, int key)i