With respect to reliance by a practitioner on the advice of a third party:
It is per se unreasonable.
It is unreasonable only if the practitioner knows the third party has a conflict of interest.
It is unreasonable if the practitioner knows or has reason to know the third person is incompetent or lacks the necessary qualifications to provide the advice.
It is unreasonable only if the practitioner has a question about whether the advice of the third party should be relied on.