Post-contractual conduct is admissible to prove the formation (existence) of a contract but not to determine its meaning (construction). A party alleging a unilateral contract arising from statements at a conference must establish sufficient certainty in the offer at the time it was made. A party is bound by the way it pleads and conducts its case at trial and on appeal, and cannot adopt an alternative legal analysis of the facts on appeal without leave, which will only be granted in exceptional circumstances.
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