bentandbroken

Does anyone know how many feet of power wire needed to run a power wire from a driverside battery through the firewall and to the driverside rear wall on a 2002 Silverado Extended cab? Trying to help out a friend out who got screwed over by a local shop, but he doesnt know what he is doing and I dont have access to the truck (or one like it). They installed RF R1200D with an 8 gauge CCA powerwire and charged him out the a$$. Im trying to save him a few bucks by not buying a full ins...