The management of Byrge Corporation is investigating buying a small used aircraft to use in making airborne inspections of its above-ground pipelines. The aircraft would have a useful life of 4 years. The company uses a discount rate of 15% in its capital budgeting. The net present value of the investment, excluding the intangible benefits, is $316,520. (Ignore income taxes.) How large would the annual intangible benefit have to be to make the investment in the aircraft financially attractive?