Phrases example - Bottom-Up Parsing

Consider the following grammar:

S : aAb
S : ABA
A : ab
A : BAB
B : aB
B : b

and the right sentential form AaaBab. The following is a partial rightmost derivation:

S => ABA
  => ABab
  => AaBab
  => AaaBab

and the following is the partially constructed parse tree:

The internal nodes in this parse tree give the following phrases:

AaaBab
aaB
aB : simple phrase
ab : simple phrase

The "handle" will be the leftmost simple phrase, i.e. aB