What language does this grammar generate? $2.(20\%)$ Remove all unit$-$productions, all useless productions, and all $\backslash$lambda $-$productions from the grammar.

$[$ S $->$ a A $|$ a B B; A $->$ a a A $|\backslash$lambda ; B $->$ b B $|$ b b C; C $->$ B $]$

What language does this grammar generate?