I have this formally defined grammar :
$$\begin{array}{rl}G=\langle&\{S,B,C\},\\&\{a,b,c\},\\&\{S\to CSB\mid CSa\mid a,B\to b\mid\epsilon,C\to c\},\\&S\rangle\end{array}$$
I know how to derive possible languages but, i have this question that i couldn't understand how to solve it because of non-terminal "$S$" symbol that exists in the right hand side:
give the left derivation starting from S to the word $w_1=cccaab$, plus the derivation tree.
How do i deal with the $S$ since it is unreachable? It would be in the result which is false. Thank you!