A number 12 copper wire has a diameter of 2.053mm. Calculate the resistance of a 31m long piece of such wire. Use rho=1.72x10-8 Ohm-m for the resistivity of copper.
This is the part that I am unsure of, all of my equations for resistivity do not really have anything along the lines of the given constants, nor can I see where one is derived. If it needs to be derived from something else, please post where you get it from so I can figure it out!