How do you solve this using a logarithm? :)

The weight of full–grown tomatoes at a farm is modeled by a normal distribution with a standard deviation of 18.4 grams. the 95 percent confidence interval for the mean weight of the tomatoes is calculated using a sample of 100 tomatoes. what is the margin of error (half the width of the confidence interval)?

How do you solve a question like this?

What set does not contain -3 the set of all real numbers the set of all integers the set of all whole numbers the set of all rational numbers