Blackbird Company sold 300 Z-tron machines in 2020 at $7,000 each. Some customers also purchased warranty contracts. Blackbird Co. uses the straight-line method for warranty revenue recognition. The total cash received by Blackbird for warranty contract sales was $120,000. The warranty contracts cover 2 years, and Blackbird estimates the total cost of servicing the contracts will be $90,000 for 2 years. In 2020, Blackbird spent $15,000 servicing the contracts. What amount of warranty revenue should Blackbird recognize in 2020 ? a. $0. b. $20,000. c. $30,000. d. $60,000 e. No revenue is recognized in this situation