Turing machine with possible transitions to the final state
I would define F(set of final states)={$q_4,q_5,q_6$} then:

$ q_4-q_5:b,b,R$

$q_4-q_7:X,X,R$ for X=a,c

$q_5-q_6:b,b,R$

$q_5-q_7:X,X,R$ for X=a,c

$q_6-q_7:X,X,R$ for X=a,b,c