Liability of guardians to pay tax, interest and penalty on behalf of incapacitated persons treated as representative liability. Where business subject to tax is carried on by a guardian, trustee or agent for a minor or incapacitated person, any tax, interest or penalty payable 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 capacitated person conducting the business, and all provisions of the Act and rules apply accordingly.