27. Let A be a set of states, and let Ac be the remaining states.

(a) What is the interpretation of

Ó Ó ç,Ñõ1 ieA j eA c

(b) What is the interpretation of

Ó Ó M V

/* 6 A c

j e A

(c) Explain the identity

Ó Ó *iPu= Ó Ó ð,ñõ

i e A j eA c

i eA c

j eA