Consider a flat wall of thickness L $=0\mathrm{.}2$m$,$ thermal conductivity k $=1\mathrm{.}2$W$/$mk$.$ And a surface area A $=15$m$^2.$ The two sides of the wall are maintained at constant temperatures T$1=120$ C and T$2=50$ C$.$ Determine:

a$)$ The value of the temperature when x$=$ L$/4$; x$=$ L$/2$ ; x$=3$L$/4$

b$)$Determine the heat flow under steady conditions.