39When royalty payable

39 When royalty payable Subject to this Part, royalty assessed by the Secretary shall be due and payable by the royalty payer on the date specified in the notice of assessment under section 22 as the date on which royalty is due and payable, being not less than 30 days after the service of the notice or, if no date is so specified or if the date specified is less than 30 days after the service of the notice, on the thirtieth day after the service of the notice.