You are investigating whether there are enough little marshmallows in a ceral box. You buy a sample of 10 cereal boxes at random. Your sample average is 100 marshmallows. Marshmallow distribution is...

You are investigating whether there are enough little marshmallows in a ceral box. You buy a sample of 10 cereal boxes at random. Your sample average is 100 marshmallows. Marshmallow distribution is Normal with a standard deviation of 20 marshmallows. You want to calculate a 95% confidence interval for the mean number of marshmellows. What is the margin of error? (Round your answer to zero decimals. ex: 15.)