3.2 Because the prices for comparable facilities management services may change over time the contract has mechanisms which the Trust can use to ensure that THC Dartford's prices remain reasonable. Every five years THC Dartford will consider with its sub-contractors the pricing of FM services. THC Dartford will then present cost proposals to the Trust which then has the option to accept the proposed charges or to request a benchmarking exercise. This benchmarking exercise will compare THC Dartford's proposed costs with comparable services in the NHS or, if appropriate, elsewhere. If the Trust and THC Dartford are then unable to agree on the pricing of THC Dartford's services the PFI contract provides for the pricing to be determined by THC Dartford competitively tendering the services between its existing and alternative sub-contractors. In making decisions about the future delivery of FM services the Trust will discuss with THC Dartford the likely demand for future services and the previous delivery record as well as pricing considerations.