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.

Let $P, Q, R$ and $S$ be the attributes of a relation in a relational schema. Let $X \rightarrow Y$ indicate functional dependency in the context of a relational database, where $X, Y \subseteq\{P, Q, R, S\}$ Which of the following options is/are always true?

In the context of relational database normalization, which of the following statements is/ are true?

Consider a relational database schema with two relations $R(P, Q)$ and $S(X, Y)$.

Let $E=\{\langle u\rangle \mid \exists v \exists w\langle u, v\rangle \in R \wedge\langle v, w\rangle \in S\}$ be a tuple relational calculus expression. Which one of the following relational algebraic expressions is equivalent to $E$ ?