Which of the following provisions are necessary for an employee's waiver of rights to be valid under the Older Workers Benefit Protection Act $($OWBPA$)$ to be valid?

Group of answer choices

The employee must receive additional compensation for signing the waiver$--$that is$,$ compensation over and above that to which they were already entitled.

The waiver must be in writing and specifically refer to the employee's rights under the ADEA.

The employee must be advised in writing to consult an attorney before the signing the waiver and to be allowed at least $21$ days to consider the matter before deciding whether to execute the waiver.

The employee must be allowed to revoke the waiver up to seven $(7)$ days after signing.

all of the above

a and b

c and d