is the union of the following four languages.
The sum of the polynomials of these 4 languages is 
We must calculate the polynomials associated with various intersections.
The sum of the polynomials of these 6 languages is 
The sum of the polynomials of these 4 languages is 
The polynomial of this languages is 
Thus 
is described by
We conclude that the inaccessible language
is described by the polynomial
which simplifies a little to yield
