During the winter of 2010-2011, the average utility bill for Delaware residents was $186 per month. A random sample of 40 customers was selected during the winter of 2011-2012, and the average utility bill was found to be $178.10 with a sample standard deviation of $22.40.
a) Using α = 0.05, does this sample provide enough evidence to conclude that the average utility bill in Delaware was lower in the winter of 2011-2012 than it was in the winter of 2010-2011?
b) What is the p-value for this test?