The Government may require the delivery of the numbered line item, identified in the Schedule as an option item, in the quantity and at the price stated in the Schedule. The Contracting Officer may exercise the option by written notice to the Contractor within ____ [insert in the clause the period of time in which the Contracting Officer has to exercise the option]. Delivery of added items shall continue at the same rate that like items are called for under the contract, unless the parties otherwise agree.