An environmental agency worries that many cars may be violating clean air emissions standards. The agency hopes to check a sample of vehicles in order to estimate that percentage with a margin of error of 4% and 99% confidence. To gauge the size of theproblem, the agency first picks 50 cars and finds 7 with faulty emissions systems. How many should be sampled for a fullinvestigation?

The environmental agency should sample at least

nothing vehicles.