Consider the spherically$-$shaped system in the figure below, comprising

a sphere enveloped in a spherical sheath of thermally conductive materials $($red

and blue$)$ and surrounded by a fluid with known convection coefficient $($h$)$ and bulk temperature

$($T$).$ The materials have conductivity k$1$ and k$2$ and radius R$1$ and R$2.$ Additionally,

the inner sphere is made of a radioactive material, which generates heat Q$1,$ and conducting

it from its center towards the blue spherical layer. Find the value of temperature

at the interface between the two materials. Explicitly state all your assumptions.