Jessica is trying to estimate where the population mean is for how many times college students engage in binge drinking inside a single month. She randomly samples 20 students from her college and measures how many times in the last month they engaged in binge drinking. She has a mean of 2.5 with a standard deviation of 3. What is the upper limit of the 95% confidence interval for the population mean of college student drinking at Jessica's college (error margin = 0.1).