(e) If the Defense Base Act is waived for some or all of the contractor’s employees, the benefits of the War Hazards Compensation Act are automatically waived with respect to those employees for whom the Defense Base Act is waived. For those employees, the contractor shall provide workers’ compensation coverage against the risk of work injury or death and assume liability toward the employees and their beneficiaries for war-hazard injury, death, capture, or detention. The contract shall provide either that the costs of this liability or the reasonable costs of insurance against this liability shall be allowed as a cost under the contract.