In the Twenty-Third century, there were multiple systems and programs for teaching dogs to read. Depending on the system, and the aptitude of the dog, it took anywhere from one to three years to teach a dog to read. It took another three to teach a dog to do arithmetic. At this time, the dog was fully qualified to work for the Planetary Postal Service. Granted, it was just the mailroom, but if the dog was clever with sorting, he could move up quickly to customer service. People liked the service dogs; they were polite and always made correct change.