Any trust account may be paid, on request, to any trustee. Unless the financial institution has received written notice that the beneficiary has a vested interest not dependent upon his surviving the trustee, payment may be made to the personal representative or heirs of a deceased trustee if proof of death is presented to the financial institution showing that his decedent was the survivor of all other persons named on the account either as trustee or beneficiary. Payment may be made, on request, to the beneficiary upon presentation to the financial institution of proof of death showing that the beneficiary or beneficiaries survived all persons named as trustees.