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 form the above $$ERD.$$ The minimum number of tables in the database is