Researchers are planning a study to investigate the environmental impact of a new anesthetic gas. They want to estimate the one year Global Warming potential per one hour surgery (GWP1) for this gas using a 95% confidence interval with a margin of error of at most 5,000 units. What sample size should they be using for their study? The standard deviation of GWP1 for anesthetic gases is known to be about 30,000 units.