Q73

Consider the following entity relationship diagram $(ERD)$, where two entities $E1$ and $E2$ have a relation $R$ of cardinality 1:m.

The attributes of $E1$ are $A11$, $A12$ and $A13$ where $A11$ is the key attribute. The attributes of $E2$ are $A21$, $A22$ and $A23$ where $A21$ is the key attribute and $A23$ is a multi-valued attribute. Relation $R$ does not have any attribute. A relational database containing minimum number of tables with each table satisfying the requirements of the third normal form ($3NF$) is designed from the above $ERD$. The number of tables in the database is