Suppose researchers announce a new vaccine for virus X. In a press release, they report that people ordinarily have a 25% chance of being infected with virus X over a 6 month period. They then describe a 6 month study where all subjects were given the new vaccine and only 20% got the virus. They don't say how many subjects were enrolled in the study, but they describe this result as statistically significant at the .05 level. Assuming the press release is accurate, we can infer that there must have been more than n subjects in the study: what is n? Use a normal approximation, and give the largest value of n supported by the press release