Is a relation from a empty set to another empty or non-empty set defined?

Q.

Find the number of empty relation we can define on a non empty set A

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Q. A relation from a non empty set $P$ to a non empty set$Q$ is always a subset of cartesian product $P\times Q.$

Q. In order that a relation $R$ defined in a non-empty set $A$ is an equivalence relation, it is sufficient that $R$

Q. In order that a relation $R$ defined on a non-empty set $A$ is an equivalence relation.
It is sufficient, if $R$

Q. In order that a relation R defined on a non-empty set A is an equivalence relation, it is sufficient, if R .......................