Which statements about the "coverage" ratio (ALLL/Non-current loans) is/are correct. a. Since about 20% of nonperforming loans eventually get charged off on average, the coverage ratio is about .2. b. Historically, the coverage ratio tends to rise in a recession because banks increase allowances for loan losses. c. Historically, the coverage ratio tends to fall in a recession because provisions for losses do not keep pace with the increase in non-current loans. d. A constant coverage ratio indicates stable loan quality