Heat is flowing through an annular wall of inside radius ro and temperature To and outside radius r1 with temperature T1. (see next page) The thermal conductivity k(T) varies linearly with temperature through this region, (a) Obtain an expression for the total heat flow through the wall evaluated at the outer surface.(b) Simplify the above result when (d is the annular thickness, much smaller than the inner radius) in which case and the geometry unravels