Let $P$ be the set of all integers from 1 to 15 . Consider any order of insertion of the elements of $P$ into a binary search tree that creates a complete binary tree. Which one of the following elements can NEVER be the third element that is inserted?

The following sequence corresponds to the preorder traversal of a binary search tree:

$$ 50,25,13,40,30,47,75,60,70,80,77 $$

The position of the element 60 in the postorder traversal of $T$ is $\_\_\_\_$ . (answer in integer)

Note: The position begins with 1.

A meld operation on two instances of a data structure combines them into one single instance of the same data structure. Consider the following data structures:

P: Unsorted doubly linked list with pointers to the head node and tail node of the list.

Q: Min-heap implemented using an array.

R: Binary Search Tree.

Which ONE of the following options gives the worst-case time complexities for meld operation on instances of size $n$ of these data structures?

You are given a set $V$ of distinct integers. A binary search tree $T$ is created by inserting all elements of $V$ one by one, starting with an empty tree. The tree $T$ follows the convention that, at each node, all values stored in the left subtree of the node are smaller than the value stored at the node. You are not aware of the sequence in which these values were inserted into $T$, and you do not have access to $T$.

Which one of the following statements is TRUE?