Figure 18-48 shows (in cross section) a wall consisting of four layers, with thermal conductivities k1=0.060 W/m.K, k3=0.040 W/m.K, and k4=0.12 W/m.K (k2 is not known). The layer thicknesses are L1
1.5 cm, L3
2.8 cm, and L4
3.5 cm (L2 is not known). The known temperatures are T1=30°C, T12=25°C, and T4
=-10°C. Energy transfer through the wall is steady.What is interface temperature T34?