Consider an ER model with the entities $E_1(A_{11},A_{12},A_{13})$ and $E_2(A_{21},A_{22},A_{23})$, where, $A_{11},A_{12},A_{13}$ are the attributes of $E_1$, and $A_{21},A_{22},A_{23}$ are the attributes of $E_2$. Let $A_{22}$ be a multi-valued attribute. $A_{11}$ and $A_{21}$ are the primary keys of $E_1$ and $E_2$, respectively.

Let $R_{12}$ be a many-to-many relationship between $E_1$ and $E_2$. Participation of both $E_1$ and $E_2$ in $R_{12}$ is total.

The minimum number of relations required to convert the ER model into relational model (assuming there is no other functional dependency) where each relation is in third normal form (3NF) is __________ . (Answer in integer)

Consider two relations r and s defined on the relational schemas R(A,B) and S(E,C), respectively. A is the primary key of R and E is a foreign key of S referencing A in R.
Which of the following operations will NEVER violate the foreign key constraint?