In this question, can't we use gauss theorem?
Let $q$ be the charge on the boundary,
Resistance between plates, $R=\dfrac{\rho_1 d_1+\rho_2 d_2}{A}$
$$E=\rho j\\ \phi=(E_2-E_1)A=\frac q {\epsilon}\\\dfrac{(\rho_2-\rho_2)}{\rho_1 d_1+\rho_2 d_2}V\epsilon=\frac qA$$
The given solution is [ this ](i.stack.imgur.com/yB2uM.png)
Let $q$ be the charge on the boundary,
Resistance between plates, $R=\dfrac{\rho_1 d_1+\rho_2 d_2}{A}$
$$E=\rho j\\ \phi=(E_2-E_1)A=\frac q {\epsilon}\\\dfrac{(\rho_2-\rho_2)}{\rho_1 d_1+\rho_2 d_2}V\epsilon=\frac qA$$
The given solution is [ this ](i.stack.imgur.com/yB2uM.png)
