An experiment was conducted to determine if the drug Prozac could be used as a treatment for the eating disorder anorexia. The test subjects were women being treated for anorexia. They were divided randomly into two groups. One group of 50 women received Prozac, and after a year 39 were deemed healthy. The second group of 40 women received a placebo, and after a year 28 were deemed healthy. Construct a 99% confidence interval for the true difference in proportion of women who were deemed healthy with taking Prozac or a placebo.