mean and variance of a dataset I have a simple question. Please see the below screenshot :

It is from a midterm exam from a university : https://cedar.buffalo.edu/~srihari/CSE555/exams/midterm-solution-2006.pdf
My questions is how the means are postive ? I am asking because the class samples are all negative so I would expect that the mean is also negative ?
It is a typo in the solution.
The author corrects it by correctly computing the Bayes discriminant in the next step.