please see the attachment.

So people, I am writing so the other who did not attend class can also have the opportunity for the extra point.

What I want? I want you to show that when two systems, 1 and 2, are brought into contact and you allow energy to flow from 1 to 2 and particles to flow from 2 to 1, the equilibrium conditions will be:

(A) t1 = t2 

(B) 1/t2 (Ds1/DN1) = 1/t1(Ds2/Dn2) 

PS.: I do not remember if when I re-wrote the condition (B) in class today I swapped temperatures 1 and 2. Anyways, the conditions above are the ones you have to find. 

PS2.: Why it is interesting to write  1/