Solve the following problem (i. e. the first attribute grammar may accept what the second attribute grammar rejects and vice versa): Augment this grammar with attributes, attribute computation functions, and predicates to reject WAE expressions which contain WITH sub-expressions with duplicate variable names in their alist. For example, the following WAE expression should be rejected:

{ +20 { with { x 2} {y 4} {x 5}} {+ x y}}}