In 1957, Wal-Noon Corp. (Wal-Noon) (plaintiff) entered into a contract to build and lease a building from Hill (defendant). Part of the building would be operated by Wal-Noon as a market, and part of the building would be subleased by Wal-Noon to other businesses. Pursuant to the lease, Hill agreed to perform all repairs to the building’s roof and its own cost and expense, except for repairs necessary for damages caused by Wal-Noon’s negligence or improper use of the building. The lease also provided that all notices, demands, consents and denials by either party should be in writing and provided to the parties at specified addresses. In 1967 or 1968, the roof of the building started leaking. Wal-Noon, at its own expense performed 12-15 repairs on the roof. Wal-Noon was then advised by roofers that the roof could no longer be repaired, but should be replaced. Wal-Noon replaced the market portion of the roof for $4,800, and the remaining portion of the roof for $4,000. At the time it replaced the roof, Wal-Noon did not read the provision of its lease providing that repairs and maintenance would be performed by Hill. Wal-Noon performed the repairs and replacement of the roof without providing notice of its actions to Hill. In 1971, Wal-Noon finally became aware of the repair provision in its lease, and requested reimbursement from Hill for the cost of replacing the roof. Hill refused to provide reimbursement, and Wal-Noon brought suit against Hill in California state court. The trial court held that Wal-Noon breached the lease agreement with Hill by failing to provide notice of the need for repairs to Hill. The trial court also held, however, that Wal-Noon was entitled to $5,867 in damages from Hill based on a theory of restitution, since Hill had been unjustly enriched. Wal-Noon appealed.