Because of inadequate public school budgets and lack of money available to teachers for classroom materials, many teachers often use their own money to buy materials used in the classrooms. A random sample of 100 public school teachers selected from an eastern state showed that they spent an average of $290 of their own money on such materials during the 2011–2012 school year. The population standard deviation was $70.
a. What is the point estimate of the mean of such expenses incurred during the 2011–2012 school year by all public school teachers in this state?
b. Make a 95% confidence interval for the corresponding population mean.