Data: ds = 20mmΦ, dc = 20mmΦ, Ls = 2m, Lc = 1.5m, P = 20kN, Es = 210 GPa and Ec = 110 GPa.

$A s=2 \times\left(\frac{\pi d_{s}^{2}}{4}\right)=2 \times\left(\frac{\pi \times 20^{2}}{4}\right)=628.32 \mathrm{mm}^{2}$

$A c=\left(\frac{\pi d_{c}^{2}}{4}\right)=\left(\frac{\pi \times 20^{2}}{4}\right)=314.16 \mathrm{mm}^{2}$

$P=P_{s}+P_{c}$

$p=\sigma_{s} A_{s}+\sigma_{c} A_{c}$

$20 \times 10^{3}=\sigma_{s} 628.32+\sigma_{c} 314.16$

$\frac{\sigma_{s} L_{s}}{E_{s}}=\frac{\sigma_{c} L_{c}}{E_{c}}$

$\frac{\sigma_{s} \times 2000}{210 \times 10^{3}}=\frac{\sigma_{c} \times 1500}{110 \times 10^{3}}$

$\sigma_{s}=1.43 \sigma_{c}$

$20 \times 10^{3}=\left(1.43 \sigma_{c}\right) 628.32+\sigma_{c} 314.16$

$\sigma_{c}=16.49 \mathrm{N} / \mathrm{mm}^{2}$

$\sigma_{s}=1.43 \sigma_{c}$

$\sigma_{s}=1.43 \times 16.49=23.58 \mathrm{N} / \mathrm{mm}^{2}$