А как вам такая задачка? Хотите голову поломать?

Consider the following grammar rules.
<Expr> ::= <IntersectExpr> | '0'
<IntersectExpr> ::= <UnionExpr> | <Intersect>
<Intersect> ::= '(' <UnionExpr> '*' <Expr> ')'
<UnionExpr> :== <RegionExpr> | <Union>
<Union> :== '(' <RegionExpr> '+' <Expr> ')'
<RegionExpr> :== <Coordinate> 'x' <Coordinate>
<Coordinate> :== '1'..'9'

Which of the following input strings correspond to the production '<Expr>'?

1) (4x8+8x4+8x8)
2) ((2x3+4x5)*0)
3) (2x3+8x98)*(2x3+0)
4) ((0*0)+2)
5) ((1..9))
6) ((4x8*4x9)+0x3