Hello, help me please with this one.

Lets $\displaystyle F $be a family of analytic functions in$\displaystyle H=\left \{ z:Imz>0 \right \} $ which holds $\displaystyle f(i)=0$ and$\displaystyle \left | f(z) \right |\leq 1$.

Find $\displaystyle \underset{f\in F}{\sup }\left | f(2i) \right |$

Thanks!