expression$->$ identifier $|$ number $|-$ expression$|($expression$)$

$(1)$

expression $$ expression operator expression

operator$->**|-|+\frac{|}{?}$

a$)$ Is the following string syntactically correct? $-(O**0)$

b$)$ Show steps of the rightmost derivation for string: $(56+67**0)$

c$)$ Is the string $(56+67**0)$ syntactically correct? Justify your answer.

d$)$ Is the grammar $G$ right or left recursive?

e$)$ Rewrite the grammar using the EBNF notation $($remove the recursion$)$