Which the following methods for determining the stage of completion of a contract involving the rendering of services are specifically referred to in IPSAS $9$ 'Revenue from Exchange Transactions' as being acceptable methods for apportioning revenue?

Please select the right answer.

Advances received to date as a percentage of the total amount receivable

Costs incurred to date as a percentage of the estimated total costs of the transaction

Revenue to date divided by total contract revenue

None of the above