Joseph on June 2 mails an offer to pay Donald $5,000 to repair a machine. The mail is received by Donald June 3rd.

Donald puts an acceptance into the mailbox June 4th. It is received by Joseph in the mail on June 7th

Before Joseph gets the acceptance from Donald, he hears that Rachael would do the job for $4,000.

Joseph calls Donald on June 5th and says " forget it"

76. When was the original OFFER effective?

77. When was the original acceptance effective??

78. When was Joseph's revocation of the offer effective?

79. Can Donald enforce the agreement or was it not successfully accepted?

80. Why or why not?