The city shall purchase an insurance plan that provides long-term disability and survivor benefits. The city shall use moneys the city would otherwise contribute to social security tax to purchase the plan. All permanent employees under the age of 70 who work 20 hours a week or more are covered by the approved plan. Coverage ceases when an employee terminates, is laid off, or participates in a work stoppage (strike or lockout). (Ord. 411 § 3, 1982).