A participant may at any time designate or change the designation of one or more primary beneficiaries and one or more contingent beneficiaries to receive any lump-sum death benefit that may be payable under the plan. The beneficiary for the lump-sum death benefit under this part may be a person, trust, or the estate of the participant. The beneficiary shall be designated on a form prescribed by the system that is received in the system’s headquarters office before the participant’s death.