The deflection of the column at $\mathrm{C}$ can be found by adding the deformations in members $\left(1\right)$ and $\left(2\right)$:

$$\begin{gathered} {\mathrm{u}}_{\mathrm{c}}={\mathrm{\delta }}_1+{\mathrm{\delta }}_2 \\ =-0.70 \mathrm{mm}+(-2.00 \mathrm{mm}) \\ =\mathbf{-}\mathbf{2}\mathbf{.}\mathbf{70}\mathbf{ }\mathbf{mm} \end{gathered}$$

Finished