With respect to each employee employed in charter activities for a street, suburban or interurban electric railway or local trolley or motorbus carrier pursuant to section 7(n) of the Act, the employer shall maintain and preserve records containing all the information and data required by § 516.2(a) and, in addition, the following:
(a) Hours worked each workweek in charter activities; and
(b) A copy of the employment agreement or understanding stating that in determining the hours of employment for overtime pay purposes, the hours spent by the employee in charter activities will be excluded and, also, the date this agreement or understanding was entered into.