Question $2$: For the beam with the cross$-$section given in the figure,

Calculate the required reinforcement and corresponding moment in the following cases, $($use the equivalent rectangular stress block assumption and equilibrium equations$)$

a$.$ Balanced reinforcement ratio ${}_b$

b$.$ Maximum reinforcement ratio $={}_{\text{m}\text{a}\text{x}}=0\mathrm{.}85{}_b$

$bw=300mm$

$h=600mm$

$d^{\text{'}}=30mm$

Material: $C\frac{30}{S}420$