13. Electric power is produced by an unregulated monopoly in a certain region. The monopolistic electric power company's production of electricity results in $10 per kilowatt hour of pollution damage to parties other than the buyers of electricity in the region. To achieve efficiency, a. a $10 per kilowatt hour corrective tax is required. b. more than $10 per kilowatt hour corrective tax is required. c. a $10 corrective subsidy is required. d. no corrective action is required