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We have seen an unambiguous context-free grammar defining the expressions over the term a and using the operators +, * (the version without parentheses). Its BNF definition is given as below: E TE+T F|T*F F Please modify the grammar to make (1) (2 points) the precedence of + higher than , and (2) (3 points) the operator + right associative. Please provide the BNF for the modified grammar. (3) (5 points) Please give the parse tree of the expression string a *a +a+a according to the modified grammar. a