3 In a cohort study of 10,000 persons, free of lung cancer that started 10 years ago, 18% were current smokers at the time of enrollment. Since enrollment, 30 persons developed lung cancer When reviewing the initial enrollment data, the researchers observed that 20 of the 30 lung cancer cases had originally been classified as "current smokers." a. Calculate relative risk of developing lung cancer comparing smokers to non-smokers. b. Interpret the results