Please provide detail explaination and core concepts$/$ lessons. $($Theory of Computation$)$

$($a$)$ Is the following CFG G ambiguous? Please justify your answer.

$($b$)$ Convert G into its equivalent Chomsky Normal Form CFG$.$

$G$: $\{\begin{array}{ccc}\text{:}[S& \text{b}\text{e}\text{g}\text{i}\text{n}\text{A}\text{e}\text{n}\text{d}& ]\\ AA\text{;}A|a|S\end{array}$