'********** multiple variable elimination 'Every lock can be opened by some key. <<$x --> lock> ==> (&&,<#y --> key>,<$x --> (/,open,#y,_)>)>. 'Lock-1 is a lock. <{lock1} --> lock>. 9 'Some key can open Lock-1. ''outputMustContain('(&&,<#1 --> key>,<{lock1} --> (/,open,#1,_)>). %1.00;0.81%')