Problems in series have been shown before, i$.$e$.,$ they require using $={\displaystyle \underset{?}{\overset{?}{}}}\frac{NL}{EA}$

A simple problem in parallel is a solid steel rod $($Esteel$=200$ GPa$)$ and concentric

copper tube $(E=100$GPa $),$ connected to a wall at one end and rigid plate on another

under an axial load $P=10kN.$ How much are the forces in the steel rod and the

copper tube and the displacement of point B$?$ For the tube: $D_{\text{o}\text{u}\text{t}\text{e}\text{r}}=25mm,D_{\text{i}\text{n}\text{n}\text{e}\text{r}}=19$

mm $.$ For the steel rod $D=12mm.$