A memory apparatus and an operation of the memory apparatus which allow quick booting are provided. A system and method can be configured to determine a price with respect to a first attribute of a first product. The second gate chain, which receives third signals generated in the first gate chain and representing the time difference, is used to provide an appropriate delay time from an input to an output depending on the time difference. In one implementation, the central tracking object is shared amongst peers in the group. The lens includes a plurality of light receiving parts fitted in the cutout portion in such a manner as to correspond to the first light emitting diodes, respectively, and a display part configured to display the light which has entered through the light receiving parts.