An interface that enables a user to determine optimum prices of products for sale. The polymer blend offers numerous advantages, including the ability to compatibilize formulations based on either polysulfide chemistry or polythioether chemistry alone. The portable security unit is linked to a device having access to a communication network. The computing device may obtain a packaging model describing a package for one or more items. The deserializer deserializes the serial test signal into the parallel test signals, and transmits the parallel test signals to a device under test. The rebate may be determined by a number of different criteria including purchase price, transaction frequency, predetermined time intervals, consumer loyalty, Point of Sale location, or any combination of these and other criteria.