let a, b be Element of Benzene; ( a = 3 \ 1 & b = 2 implies ( a "\/" b = 3 & a "/\" b = 0 ) )
assume A1:
( a = 3 \ 1 & b = 2 )
; ( a "\/" b = 3 & a "/\" b = 0 )
then
( a in {0,1,(3 \ 1),2,(3 \ 2),3} & b in {0,1,(3 \ 1),2,(3 \ 2),3} )
by ENUMSET1:def 4;
then reconsider aa = a, bb = b as Element of B_6 by YELLOW_1:1;
( aa "\/" bb = 3 & aa "/\" bb = 0 )
by A1, Th15;
hence
( a "\/" b = 3 & a "/\" b = 0 )
by Th14; verum