(1) A disclaimer is not valid unless it complies with all of the following:

    (a) Is in writing.

    (b) Declares the disclaimer.

    (c) Describes the disclaimed interest.

    (d) Is signed by the disclaimant.

    (e) Is delivered as provided in sections 2904, 2905, and 2906.

    (2) If a disclaimable interest is disclaimed by a fiduciary on behalf of the person to whom the disclaimable interest devolves, the disclaimer must be signed by all incumbent fiduciaries. Unless the governing instrument requires otherwise, a disclaimer of a disclaimable interest by a trustee may be signed by less than all incumbent trustees. A disclaimer of a fiduciary power by a fiduciary may be signed by less than all incumbent fiduciaries.