$(25$p$)$

In the figure, a circular cross$-$section rod with a diameter of $4cm,$ made of material with

number $1,$ is placed inside the pipe produced from material with number $2.$ The entire

system is mounted on a rigid plate from below and on a fixed wall from above. The

temperature when the system is installed is $10C.$ How much should the temperature be

changed to close the $0\mathrm{.}0Kcm$ gap?

$($K value $=23)!$