On September 1, Stan mailed Roger an offer with definite and certain terms and that was legal in all respects stating the offer was good for ten days. Four days later, Stan sent Roger a letter by certified mail (time stamped by the Postal Service at 12:00 p.m.) stating that the original offer was revoked. That afternoon around 1:30 p.m. Roger e-mailed Stan accepting the offer. Stan then immediately phoned Roger to tell Roger that he had revoked the offer earlier that afternoon, and he would surely receive it in tomorrow's mail. Was the offer revoked by Stan? Why or why not?