Both a) and b) have to follow a negotiated settlement.
Clearly, if there was unconditional withdrawal, there would be no b).
And, of course, I made no such generalisation.
I have always particularly disliked Sharon and, if I was Israeli I would certainly vote Labour. However, in this case, I hope that you're wrong.
Initially anti, Ariel Sharon now champions the Israeli withdrawal from Gaza. This would be a start. Also, Sharon may be the best chance of 'selling' any settlement to the Israeli right.