USA
33 Certainty
1. Even though a manifestation of intention is intended to be understood as an offer, it cannot be accepted so as to form a contract unless the terms of the contract are reasonably certain.
2. The terms of a contract are reasonably certain if they provide a basis for determining the existence of a breach and for giving an appropriate remedy.
3. The fact that one or more terms of a proposed bargain are left open or uncertain may show that a manifestation of intention is not intended to be understood as an offer or as an acceptance.
34 Certainty and Choice of Terms; Effect of Performance or Reliance
1. The terms of a contract may be reasonably certain even though it empowers one or both parties to make a selection of terms in the course of performance.
2. Part performance under an agreement may remove uncertainty and establish that a contract enforceable as a bargain has been formed.
3. Action in reliance on an agreement may make a contractual remedy appropriate even though uncertainty is not removed.
204 Supplying an Omitted Essential Term
When the parties to a bargain sufficiently defined to be a contract have not agreed with respect to a term which is essential to a determination of their rights and duties, a term which is reasonable in the circumstances is supplied by the court.

