A vendor shall not be allowed to substitute material, supplies, equipment, or services from that offered; provided, however, if the material, supplies, equipment, or services offered are no longer available to the vendor for reasons beyond its control, the Agent may consider a request by the vendor for substitution. All such requests must be in writing, must set forth the reasons the product or service is no longer available, and if requested, must be accompanied by samples, record of performance, certified copies of tests by impartial and recognized laboratories, and such additional data as the Agent may request. Samples and data shall be furnished sufficiently in advance to allow for investigation before a decision is made. If the change is approved, the vendor shall warrant that the substitute article is equal to or better than the specified article. If the change results in any cost savings to the vendor, the cost savings shall be reflected in full and cause a reduction in price to the County.