Sentence:  A 5 - percent royalty is paid on any production during the period the contract is in effect ; if the Government certifies that production may be possible from the property , the royalty obligation continues for the 10 - year <WSD>period</WSD> usually specified in the contract or until the Government 's contribution is repaid with interest . 
Meaning of the word marked with <WSD> tags:  an amount of time