. . On January 1 of the current year, the balance sheet of PharmaTech Corporation included patents with a carrying value of $25 million. During the current year, the following transactions took place related to the company's patents: $4 million in legal costs defending patents that were challenged in infringement suits, $2 million of which was for the successful defense of a patent. $5 million in research costs, $3 million in development costs, and $1 million in legal fees related to a new drug that was granted a patent during the year As a result of the above transactions, the December 31 carrying value of the patents before amortization or impairment under U.S. GAAP is: Oa: 530 million Ob. 536 million Oc. $28 million Od. $31 million