11 :-
                   <ul>
                     <li> 
                       forall(W,forall(X,not o__chk11(W,X))) :-
                       <ul>
                         <li> 
                           forall(X,not o__chk11(B │{B\=light_on},X)) :-
                           <ul>
                             <li> 
                               not o__chk11(B │{B\=light_on},C │{C#=<0}) :-
                               <ul>
                                 <li> 
                                   