A professional employee in a large corporation receives an average of μ=41.7 e-mails per day. Most of these e-mails are from other employees in the company. Because of a large number of e-mails, employees find themselves distracted and are unable to concentrate when they return to their tasks. In an effort to reduce distraction caused by such interruptions, one company established a priority list that all employees were to use before sending an e-mail. One month after the new priority list was put into place, a random sample of 45 employees showed that they were receiving an average of x = 36.2 e-mails per day. The computer server through which the e-mails are routed showed at σ=18.5. Has the new policy had any effect? Use 5% level of significance to tst the claim that there has been a change in the average number of e-mails received per day per employee.

So I took out the numbers:
μ = 41.7 | x = 36.2 | σ=18.5 | ∝ = .05

I'm having trouble with making a hypothesis and once I get over that I should be able to do the calculations, I would greatly appreciate the help... someone please?