Consider a medium in which the heat conduction equation is given in its simplest forms as $(10$ pts$)$

$\frac{1}{r^2}\frac{\text{d}\text{e}\text{l}}{\text{d}\text{e}\text{l}\text{r}}(r^{\text{d}\text{e}\text{l}}\frac{\text{d}\text{e}\text{l}\text{T}}{\text{d}\text{e}\text{l}\text{r}})=\frac{1}{}\frac{\text{d}\text{e}\text{l}\text{T}}{\text{d}\text{e}\text{l}\text{t}}$

$($a$)$ Is heat transfer steady or transient? Why?

$($b$)$ Is heat transfer one$-,$ two$-,$ or three$-$dimensional? Why

$($c$)$ Is there heat generation in the medium? Why

$($d$)$ Is the thermal conductivity of the medium constant or variable? Why

$($e$)$ Is the medium a plane wall, a cylinder, or a sphere? Why

Just write one sentence to answer "Why".