Heat and Mass Transfer in Food Processing

A food package wall consists of two layers: plastic film of thickness $L_1 = 0.002\text{ m}$ ($k_1 = 0.2\text{ W/(m}\cdot\text{K)}$, thermal resistance $R_1 = L_1/k_1 = 0.01\text{ m}^2\cdot\text{K/W}$) and cardboard of thickness $L_2 = 0.004\text{ m}$ ($k_2 = 0.08\text{ W/(m}\cdot\text{K)}$, $R_2 = 0.05\text{ m}^2\cdot\text{K/W}$). Total conductive resistance $R_{total} = R_1 + R_2$ in $\text{m}^2\cdot\text{K/W}$ is: