Electric field and Plate (part 2)

Find the electric field in the $z$ direction due to a plate of area charge density $\lambda$ at a distance $a$ above the plate.. $\angle B=8°$ If your answer comes in the form of $E(\vec{k})=\alpha \frac{\lambda}{\epsilon_{0}}$
Find $100 \alpha=?$
Details and Assumptions
1) The triangle is isosceles .
2) $AB=BC=100$
3) $a=0.5$
4) $\epsilon_{0}$ is electric permittivity .
5) The triangle is in $xy$ plane
6) Distance $a$ is measured from $B$ and is perpendicular to $xy$ plane.
7) Cosider B as origin. Right side $+x$ axis and in forward $+y$ axis.