A wall is made from an inhomogeneous (nonuniform) material for which the thermal conductivity varies through the thickness according to \( k=a x+b \), where \( a \) and \( b \) are constants. The heat flux is known to be constant. Determine expressions for the temperature gradient and the temperature distribution when the surface at \( x=0 \) is at temperature \( T_{1} \). (Ans: \( T=T_{1}+\frac{q_{x}}{a} \ln \frac{b}{a x+b} \) )