Herd immunity depends on the fraction of a population that possesses antibodies to a disease. In this problem, you will determine the minimum population fraction, at the 99% confidence level, that does so, if in a random sample of 56 people, 17 test positive for the antibody. (Use the normal distribution as the approximation to the binomial distribution, and use the estimate p = p in calculating the confidence interval.) Express your answer as a percentage to one decimal place; that is, fill in the blank for the following statement: "at a 99% confidence level, at least __% of the population possesses the antibody."