Vinson Company purchased a patent for $180,000 at the beginning of Year8, and estimated that its expected useful life was 5 years from the purchase date. The patent has a legal life of 20 years. What amount should be recorded as amortization expense for the patent in Year8?

a. $9,000 b. $36,000 c. $18,000 d. $72,000 e. $180,000