Consider the function $$f(x)=\frac{x}{ \sqrt{4 - x^2}}$$

a) Determine the domain of the function.
Note: Write the answer in interval notation. If the answer involves more than one interval write the intervals separated by the union symbol, U. If needed enter $\infty$ as infinity and $- \infty$ as - infinity .
Domain =

b) Find the vertical asymptote(s). If there is more than one vertical asymptote give a list of the $x$-values separated by commas. If there are no vertical asymptotes type in None .

$x =$