Daniel Hardware Co. is considering alternative financing arrangements for equipment used in its warehouses. Besides purchasing the equipment outright, Daniel is also considering a lease. Accounting for the outright purchase is fairly straightforward, but because Daniel has not used equipment leases in the past, the accounting staff is less informed about the specific accounting rules for leases. The staff is aware of some lease rules related to a "90 percent of fair value," "75 percent of useful life," and "residual value deficiencies," but they are unsure about the meanings of these terms in lease accounting.

(b) An important element of evaluating leases is determining whether substantially all of the risks and rewards of ownership are transferred in the lease. How is "substantially all" defined in the authoritative literature?