On May 1 Ralph offers to cure and smoke Sam's pork, and promises to keep the offer open until June 1. On May 3 Ralph mails Sam a letter revoking the offer. Sam receives and reads the letter on May 5 and responds to Ralph on May 6 (assume this is the FIRST and only contact Sam has had with Ralph). Ralph's revocation of the offer became effective on:

May 5.

May 3.

no date because the offer is irrevocable.

May 6.