How many fire extinguishers on-board?

We have the standard that came with the unit by the entry door. We also have one twice as large in the front closet within arms reach of the bed. I also have one in the truck cab that is accessible from the drivers seat of the truck. The number one cause of RV fires is the refrig. I wonder what it would cost for manufacturers to install one of these in the refrig compartment. It would probably reduce insurance cost, too. Phillip
http://www.ebay.com/itm/NEW-FIREBOY-125-CUBIC-FT-AUTOMATIC-FIRE-EXTINGUISHER-/250610870593?hash=item3a59926941&vxp=mtr

Look t this fire video....fridge fire.
http://www.youtube.com/watch?v=J-AjXk7I3XM

There are plenty more on YouTube