A steel beam supported by three parallel pin-jointed steel rods is shown in the figure. The moment of inertia of the beam is $8 \times 10^{7} \mathrm{~mm}^{4}$. Take modulus of elasticity of steel as $210 \: \mathrm{GPa}$. The beam is subjected to uniformly distributed load of $6.25 \: \mathrm{kN} / \mathrm{m}$, including its self-weight.
The axial force (in kN ) in the centre rod CD is $\_\_\_\_\_\_\_\_\_\_\_\_$ (round off to one decimal place).
