Section 38. After the entry of a decree authorizing or licensing an executor, administrator, guardian, conservator or trustee to sell real estate at a public or private sale, provided: (a) the notice of the petition for license to sell real estate and of the time and place appointed for hearing, the same shall have been given by publication at such times and in such newspapers as the court orders, and (b) there shall have been no appearance entered against such sale prior to the entry of the decree or where such appearance shall have been entered and withdrawn prior to the entry of the decree, notwithstanding the fact that an appeal may have been taken prior to the expiration of the period allowed for an appeal therefrom, it shall be conclusively presumed that the amount of the advantageous offer stated in said petition for license to sell real estate is the highest possible price obtainable for the real estate described in such petition and that the executor, administrator, guardian, conservator, or trustee has fully satisfied his fiduciary duty to obtain the highest possible price for such real estate.