The following is my answer to the problem 9.45 page 290 from the book "Business Statistics A First Course" by David M. Levine, Timothy C. Krehbiel and Mark L. Berenson

The Problem

You are the manager of a restaurant that delivers pizza to college dormitory rooms. You have just changed your delivery process in an effort to reduce the mean time between the order and completion of delivery from the current 25 minutes. From past experience, you can assume that the population standard deviation is 6 minutes. A sample of 16 orders using the new delivery process yields a sample mean of 22.4 minutes.

A) At the 0.05 level of significance, is there evidence that the mean delivery time has been reduced below the previous population mean value of 25 minutes?

Z critical value from the table for α=0.05 is -1.64; -1.73 < -1.64 so the null hypothesis is rejected.
The Problem

You are the manager of a restaurant that delivers pizza to college dormitory rooms. You have just changed your delivery process in an effort to reduce the mean time between the order and completion of delivery from the current 25 minutes. From past experience, you can assume that the population standard deviation is 6 minutes. A sample of 16 orders using the new delivery process yields a sample mean of 22.4 minutes.

A) At the 0.05 level of significance, is there evidence that the mean delivery time has been reduced below the previous population mean value of 25 minutes?

There is evidence that the mean delivery time is less than 25 minutes.