The beam section shown below is made from with $($:$k_1=0\mathrm{.}85\}$ and $S500)=(500$MPa.

a$.$ What is the balanced tension steel $A_{sb}($for bending$)$ of this section?

b$.$ Determine the bending moment capacity $M_r$ of the section when $A_s=A_s^{\text{'}}=820,$ using ${}_{mc}=1\mathrm{.}0{}_{ms}=1\mathrm{.}0.($Hint: You must calculate the actual moment capacity without reducing material strengths by the $$ factors.$)$