Bustang wrote:Classic view of K's: Revoke at anytime before acceptance. RS 2d 42/Peterson v. Pattberg.
Modern view of K's: B's walk was sufficient to constitute "substantial performance" as the court defined in Cook v. Coldwell.
D will likely argue that walking to the end of the bridge wasn't consideration, but simply a condition for a gratuitous promise(Plowman). P will argue along the ruling set in Batsakis/Sidley that D "got what he bargained for", P incurred legal detriment, and now the detriment should induce the promise (giving P $100).
I know this doesn't answer your question.
I think it does actually. It all depends on if you are going old school or new school as to when a unilateral contract can be revoked. Old school says it can be revoked up until full completion. New school all depends on how much/to what extent the promisee has accomplished. If it thus deemed that the promisee has fallen under the substantial performance umbrella (which depends on criteria and circumstance), then there is a contract and it cannot be revoked.
so to answer your question, regardless of which school you apply, there was a valid contract because B fully crossed the line. he performed the action in full before the wind pushed him back.
at least i hope im right, or else i need to look over my k notes.