I am struggling with this question:

The customer service desk at Company X answers phone calls in an average of 5 minutes (H0: u=5). After instituting a new training program, the company believes that the average time to answer a call has decreased (HA: u<5).The significance level is 5% (0.05) and the power of the test when is 0.85. Before the sample is collected, the probability that the analyst fails to reject the null hypothesis when, in reality, u=3 , is equal to ______.




Any and all help is greatly appreciated.