In a webpage I saved from long time ago:
Many people are happy when they purchase their first scanner because they can now attach images to the Email they send to friends and family. Little do they know that the art of scanning photographs into clear, crisp image files of a small size (50 KB or less) requires skill and an understanding of their scanner hardware and image editing software.
(NOTE: The small file size as given above is recommended because it only requires about 10 seconds to transmit a file of this size through their modem; hence, neither sender nor receiver will grow impatient waiting. The 10 second time is calculated as follows for a typical 56.6 Kbps modem connection: 50 KBytes x 8 bits/Byte / 40,000 bits/sec = 10 sec. The discussion below reveals that if you're not careful, you could easily spend 100 times longer than the above 10 seconds waiting for the file to transmit to the recipient!)
I wonder where "40,000 bits/sec" comes from in the calculation for the time for transmission? it isn't equal to "56.6Kbps". Or am I missing something?