Jackson paid brady $700 for a 90 day option to purchase brady's 160 acre farm for $132,000. the option agreement was in writing and signed by both parties. the agreement referred only to the option, its period, a legal description of the farm, and the purchase price. thirty days later, jackson wrote brady, "i hereby exercise my option to purchase your farm for $132,000, subject to your replacing the well pump and related plumbing fixtures." is there a contract? is the option still valid?