A composite wall consists of two solid rectangular layers in direct thermal contact, placed between a hot reservoir at constant temperature \(T_H\) and a cold reservoir at constant temperature \(T_C\). Layer 1 has thickness \(L_1\) and thermal conductivity \(k_1\), while Layer 2 has thickness \(L_2\) and thermal conductivity \(k_2\). Both layers have the same cross-sectional area \(A\) perpendicular to the heat flow, and heat transfer occurs only along the direction of thickness under steady-state conditions. Which of the following expressions correctly represents the rate of thermal energy transfer \(\dfrac{Q}{\Delta t}\) through the composite wall?