Given the beam cross$-$section in Figure $1$ and the material strengths in Table $1,$ please find:

$M_{CR}$ and ${}_{CR}($Negative bending so the top fiber is in tension$)$

Steel stress before and after cracking $(=\frac{A_s}{b_w}d)$

Curvature after cracking when $M=M_{CR},M_y,$ and ${}_y$

Table $1-$ Material strengths