According to one embodiment, a method comprises receiving one or more images comprising at least one response device, each response device having an identifier identifying the response device and two or more response indicators. The method further comprises identifying, by the respective identifier, one or more response devices in the one or more images, and determining, for each identified response device, a response based on an absence of one or more response indicators of the response device in at least one of the one or more images.
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