Answer
$385.6 km/deg$
Work Step by Step
a) We use the definition of sine as the opposite side divided by the hypotenuse, and isolate $h$.
b) we just have to derivate $h$ with respect to theta (if you don't remember the derivative of $csc(x)$, just write it as $[sin(x)]^{-1}$ and use power rule combined with chain rule). We just put $theta=30°$ and find the answer in $km/radian$, then we convert radian to degree.
All these steps are done on the image below.
