(1) The United States may, in a civil action, recover a civil penalty from any person who knowingly engages in conduct prohibited by section 53 of this title. The amount of such civil penalty shall be

(2) The United States may, in a civil action, recover a civil penalty from any person whose employee, subcontractor or subcontractor employee violates section 53 of this title by providing, accepting, or charging a kickback. The amount of such civil penalty shall be the amount of that kickback.

(1)  the date on which the prohibited conduct establishing the cause of action occurred, and

(2)  the date on which the United States first knew or should reasonably have known that the prohibited conduct had occurred.