(Disp | 'coin.coke.Stud)\{coin,coke}

--- tau ---> (('coke.Disp + 'sprite.Disp) | coke.Stud)\{coin,coke}

(Disp | coke.Stud)\{coin,coke}

None.

(('coke.Disp + 'sprite.Disp) | coke.Stud)\{coin,coke}

--- tau ---> (Disp | Stud)\{coin,coke}
--- 'sprite ---> (Disp | coke.Stud)\{coin,coke}

StudentImpl

--- 'study ---> (Disp | 'coin.coke.Stud)\{coin,coke}

(Disp | Stud)\{coin,coke}

--- 'study ---> (Disp | 'coin.coke.Stud)\{coin,coke}