4. A large flat wall with a thickness of 50cm has a thermal conductivity of k=25W/mK. It has a constant surface temperature T0 and a uniform heat flux q0 on the left surface (x=0). When the surface temperature is on the right surface TL=225C and the ambient temperature is 25C, heat transfer occurs on the right surface via convection and radiation. On the right surface, the emissivity and the convection heat transfer coefficient are 0.7 and 15W/m2K, respectively. Obtain a relationship for the variation of temperature and determine the temperature of the left surface of the wall at x=0