It must be a regular language, L = {w | w ∈ a*b*a* and |w| > 5}.
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another approach:
L can be represented as follows:
L = {w| w ∈a*b*a*} - {w | w ∊ a*b*a* and |w| <= 5}.
It is clear that {w| w ∈a*b*a*} is a regular language.
Now since the language {w | w ∊ a*b*a* and |w| <= 5} contains a finite number of strings in it, we can say that it is also regular.
Since regular languages are closed under difference, L must be regular.
