1 | 6. k: ||tr|| 7. a delivered at time k 8. k': ||tr||. b delivered at time k'  loc(E)(tr[k']) = loc(E)(tr[k])  k k' 9. k: ||tr||.
a delivered at time k 
( k': ||tr||. k' < k & c delivered at time k' & loc(E)(tr[k']) = loc(E)(tr[k])) 10. k: ||tr||.
c delivered at time k 
( k': ||tr||. k' < k & b delivered at time k' & loc(E)(tr[k']) = loc(E)(tr[k])) False |