A dissenting trustee who has joined another trustee in exercising a power is not liable to the beneficiaries or to others for the consequences of the exercise of the power if the dissenting trustee joins because of a requirement for unanimous trustee consent to the exercise of the power. The dissenting trustee's dissent must be presented in writing to a co-trustee and a legally competent beneficiary or, if the beneficiary is a minor or an incompetent person, the representative of the beneficiary. A trustee who is not authorized to exercise a power is not liable to the beneficiaries or to others for
(1) the exercise by a co-trustee of the power; or
(2) the failure to exercise that power.