How large of a sample is needed so that the margin of error is within (+/-) 1.6 for a 95% confidence level?

How large of a sample is needed so that the margin of error is within (+/-) 1.6 for a 95% confidence level?

Earlier in the question parts it says the the odor threshold for DMS in trained wine tasters is about 25 micrograms per liter of wine. The untrained noses of consumers may be less sensitive, however. For 10 untrained students here are their thresholds 31, 31, 43, 232, 34, 32, 20, 24. Standard deviation of 6.8