In the provided grammar, A is defined as A -> S + T. In step 4, the assumption is to replace A -> S + T with the following productions: A -> SA1, SA1 -> + A2, A2 -> TA3. Is this correct?
I'd also like to ask if we introduce a new variable "Z", the introduction of the new variable is permissible, and it can be designated by any letter of the alphabet, provided it does not conflict with existing variables within the grammar?