(a) That's correct. Section 23 of the ACL makes void any unfair term or terms in a standard form consumer contract or small business contract.

Provided that it is possible for the contract to continue operating without the unfair terms (i.e. if its remaining terms are sufficiently complete) then the contract continues to bind the parties.

In the present case, treating the unfair term as void does not render the whole contract inoperable.  A could enforce the contract, and seek appropriate relief for breach of contract.