Liability of guardians and trustees: personal liability for tax, interest and penalties when managing business for incapacitated persons. Where a business is carried on by a guardian, trustee or agent for a minor or other incapacitated person, the liability for tax, interest or penalty shall be levied upon and recoverable from that guardian, trustee or agent in the same manner and to the same extent as if the minor or incapacitated person were a major and conducting the business himself, with all provisions of the Act and rules applying accordingly.