(dissenting)—This case concerns a lease for 49 years with an option for 20 years—69 years—with a rent escalation clause based upon a nonexistent index. To enforce the lease with no consideration for the diminishing value of the dollar, and the accepted fact of the rising cost of existing, borders on the unconscionable as it relates to the beneficiaries of a trust whose counsel made a mistake. The lease as originally drafted in 1958 was impossible of performance because the measure for escalation of the rent was nonexistent. Consequently, no contract was created at that time, see Restatement of Contracts §§ 5014 and 4565 (1932). At best, the lessees, were month-to-month tenants. See RCW 59.04.020; Ryan v. Lambert, 49 Wash. 649, 96 P. 232 (1908). Neither the 1963 partition nor the 1969 Herrmann settlement altered that situation. They merely altered the method and amount for the payment of rent. If the bank terminates the tenancy, then the "tenants" are entitled to restitution in accordance with Restatement of *840Restitutions § 42(3) (1937),6 and its attendant comment. The choice is the bank's—either to continue under the existing month-to-month tenancy at $402.50 per month for 69 years, or to terminate the tenancy and pay restitution to the tenants up to the value of the improvements.
Petition for rehearing denied August 15, 1977.
Review denied by Supreme Court February 17, 1978.
"Mistake prevents the existence of a contract in accordance with the rules stated in §§ 51, 71, 456; and prevents the discharge of a duty or an effective assignment in accordance with similar rules."
" Except as stated in § 455, or where a contrary intention is manifested, a promise imposes no duty if performance of the promise is impossible because of facts existing when the promise is made of which the promisor neither knows nor has reason to know."
"A person who has acquired an interest in land or chattels as the result of an agreement with the owner made under a mistake of fact and avoided by the owner is entitled to restitution for the value of services rendered in their preservation or in making appropriate improvements thereon."