A July 2020 article in the New England Journal of Medicine reports the results of a randomized trial designed to assess the efficacy of Hydroxychloroquine in preventing Covid-19 infection in persons exposed to others with Covid-19. There were 821 subjects enrolled in this study. Of the 414 randomized to the treatment (Hydroxychloroquine) arm, 49 (11.8%) developed Covid (or probable Covid) within 14 days of randomization. Of the 407 randomized to the placebo arm, 58 (14.3%) developed Covid (or probable Covid) within 14 days of randomization. Estimate (and report) a 95% CI for the population proportion of persons treated with Hydroxchloroquine who would develop Covid (or probable Covid) within 14 days of randomization. a. (-15%, -8.6%) b. (-15%, 8.6%) c. (8.6%, 15%) d. (15%, -8.6%)