reserve x,y,c for set;

theorem
  for x,y,c being non pair set for s being State of BorrowCirc(x,y,c)
  for a1,a2,a3 being Element of BOOLEAN st a1 = s.x & a2 = s.y & a3 = s.c holds
Following(s,2).BorrowOutput(x,y,c) = 'not' a1 '&' a2 'or' a2 '&' a3 'or' 'not'
  a1 '&' a3 by Lm2;
