(1) Remuneration for work is deemed to be tacitly agreed if the production of the work, in the circumstances, is to be expected only in return for remuneration.
(2) If the amount of remuneration is not specified, then if a tariff exists, the tariff remuneration is deemed to be agreed; if no tariff exists, the usual remuneration is deemed to be agreed.
(3) In case of doubt, remuneration is not to be paid for a cost estimate.