$EI ~ \theta_{AB} = 0$
$\frac{1}{2}(\frac{1}{2}L)(\frac{1}{4}w_oL^2) - \frac{1}{2}L(M_{wall}) - \frac{1}{3}(\frac{1}{2}L)(\frac{1}{8}w_oL^2) = 0$
$\frac{1}{16}w_oL^3 - \frac{1}{2}M_{wall}L - \frac{1}{48}w_oL^3 = 0$
$\frac{1}{2}M_{wall}L = \frac{1}{24}w_oL^3$
$M_{wall} = \frac{1}{12}w_oL^2$ answer
Note that the actual bending moment is a negative moment (bending the beam downward) as shown in the figure. The answer above is positive which indicates that our assumption of downward arrows is correct. Had we assumed positive Mwall (upward arrows), the answer would be negative pointing out that the actual moment is negative (or downward arrows).
$\delta_{max} = t_{A/B}$
$EI ~ \delta_{max} = EI ~ t_{A/B}$
$EI ~ \delta_{max} = (Area_{AB}) \cdot \bar X_A$
$EI ~ \delta_{max} = \frac{1}{2}(\frac{1}{2}L)(\frac{1}{4}w_oL^2)[ \, \frac{2}{3}(\frac{1}{2}L) \, ] - \frac{1}{2}L(M_{wall})[ \, \frac{1}{2}(\frac{1}{2}L) \, ]$
$~ ~ ~ ~ ~ ~ ~~~~ ~~~ ~ ~ ~ - \frac{1}{3}(\frac{1}{2}L)(\frac{1}{8}w_oL^2)[ \, \frac{3}{4}(\frac{1}{2}L) \, ]$
$EI ~ \delta_{max} = \frac{1}{16}w_oL^3(\frac{1}{3}L) - \frac{1}{2}M_{wall}L(\frac{1}{4}L) - \frac{1}{48}w_oL^3(\frac{3}{8}L)$
$EI ~ \delta_{max} = \frac{1}{48}w_oL^4 - \frac{1}{8}M_{wall}L^2 - \frac{1}{128}w_oL^4$
$EI ~ \delta_{max} = \frac{1}{48}w_oL^4 - \frac{1}{8}(\frac{1}{12}w_oL^2)L^2 - \frac{1}{128}w_oL^4$
$EI ~ \delta_{max} = \frac{1}{48}w_oL^4 - \frac{1}{96}w_oL^4 - \frac{1}{128}w_oL^4$
$EI ~ \delta_{max} = \frac{1}{384}w_oL^4$ answer