Obtain transfer resistances and use them to find these two currents

[s3a]

Homework Statement

The problem that this thread is about is problem 4.5 which is in the 4.5.jpg file (which makes reference to problem 4.2 which is in the 4.2.jpg file).

Homework Equations

$R_{transfer,ij}$ = $Δ_R$ / $Δ_{ij}$

The Attempt at a Solution

This concept of "transfer resistance" seems to be something not discussed frequently. I checked my other book for that term/concept and, I couldn't find anything. When I check online, I find many not-directly-related things in the field of heat transfer.

Am I correct in thinking that it is, basically, an equivalent resistance of a certain segment of an electrical circuit (or all of it) defined to be located at a certain point in the electrical circuit?

While it makes some sense to me that R = V/I = V/(V $Δ_{12}$ / $Δ_R$) = $Δ_R$ / $Δ_{12}$ because this derivation is similar to the derivation of the previous problem (4.4) in my book, I do not understand what is going on.

I suppose I understand how to do this problem, computationally but, I don't truly know what it is I'd be doing if I just blindly computed things. Assuming I understand what a transfer resistance is (from what I said above), how do I know where in the electrical circuit to define each equivalent resistance?

Any input would be greatly appreciated!

 

[s3a]

If I did not include enough information, someone please tell me so that I can incude it.