Please explain the answer step by step

3. The following language L over A = {a, b): is not context-free. Find an unrestricted (Chomsky type "0") grammar generating it. Hint: First, a string amen #Abamb can be generated (# is a special symbol erased at the end of generation). Then symbols b can be copied one after another to the right end of the string moving the symbol # to the left for each copied symbol b until # reaches symbols a (and is erased)