In Pleger v. Bouwman, 61 Mich App 558, 560; 233 NW2d 82 (1975), the plaintiffs orally notified the defendants of their intent to exercise their option and the defendants proceeded to obtain title insurance, have their attorney prepare closing papers, and arrange a closing meeting. The defendants did not appear at the closing meeting and, at that point, complained that the plaintiffs had not exercised their option in writing. Under those circumstances, this Court applied equitable estoppel and enforced the option, but did not find that oral notification was acceptable on its own. Id., pp 560-561.