$AB \perp CD$, $AE\perp CB$, $CE = BE$, $BE = a$, $FE = b$
In the first few parts of the question I've answered the following:
$AF = AD$
$FE = GE$
$R = \frac{a^2+b^2}{2b}$
The last part of the question, the one I'm having trouble solving, is finding $FH$.
Thanks.