On May 1 Raj Offers to Staff Sam's Sandwich Shop

On May 1 Raj offers to staff Sam's Sandwich Shop with food preparers and servers for a certain price,and promises to keep the offer open until June 1.On May 3 Raj mails Sam a letter revoking the offer.Sam receives the letter on May 5 and responds on May 6.Raj's revocation of the offer became effective on

A) May 3.
B) May 5.
C) May 6.
D) no date because the offer is irrevocable.