Multiple TV out from single Macbook Pro
a) You can't output 10 different video signals on your single HDMI output. Besides limitation of the graphic card of your computer, that would also require generating/reading 10 different video streams from your computer. One possible option, depending on your project aim and structure, is to produce 1 hi definition video stream from your computer and use an external tool to tile/scale it in 10 different screens (something like http://www.ambery.com/2x2hdvgaviwa.html)

b) sending same video to all 10 screens only requires that you have a one input/ten outputs HDMI splitter (assuming your ten screens have a HDMI input).