Given that,
$R \rightarrow$ equivalence relation on a set $A$
Let $A=\{a, b, c, d, e, f\}$
Since, $R$ is an equivalence relation on set $A$, then it must be satisfies reflexive property, for this.
$a R a, \forall a \in A$
That inean minimum number of elements in 'R' should be six
eg, $R=\{(a, a),(b, b),(c, c),(d, d) (e, e),(f, f)\}$