Where the business in respect of which tax is payable under this Act is carried on by, or is in charge of, any guardian, trustee or agent of a minor or other incapacitated person on behalf of and for the benefit of, such minor or other incapacitated person, the taxshall be assessed upon and recoverable from such guardian, trustee or agent, as the case may be, in the manner and to the same extent as it would be leviable upon and recoverable from any such minor or incapacitated person, if he were of full age and sound mind, and if he were conducting the business himself and all the provisions of this Act shall apply accordingly