'***** second variable introduction (induction) 'if something opens lock1, it is a key < (/,open,$1,_)> ==> <$1 --> key>>. 'lock1 is a key lock>. 7 'there is a lock with the property that when opened by something, this something is a key (induction) ''outputMustContain('<(&&,<#1 --> (/,open,$2,_)>,<#1 --> lock>) ==> <$2 --> key>>. %1.00;0.45%')