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 95% confidence. To gauge the size of the problem, the agency first picks 50 cars and finds 11 with faulty emissions systems. How many should be samples for a full investigation?

The agency should sample at least ___ vehicles. (Round up to nearest whole number)