Kayla Greene is a team lead for an environmental group for a certain region. She is investigating whether the population mean monthly number of kilowatt hours (kWh) used per residential customer in the region has changed from 2006 to 2017. She is concerned that changes such as more efficient lighting and the increased use of electronics and air conditioners are affecting the population mean monthly number of kilowatt hours consumed per residential customer. Kayla assumes the population standard deviation for 2006 and 2017 using the data that was provided to her by local utility companies. Using data that was collected by her environmental group, Kayla selects a random sample of residential customers who were active for all of 2006 and a separate sample of residential customers who were active for all of 2017. The population standard deviations and the results from the samples are provided in the accompanying table. Assuming the conditions needed for the hypothesis test have been met, what is the z test statistic for this hypothesis test, rounded to two decimal places?

2006 2017

x1=894.7kWh x2=910.2kWh

n1=361 n2=424

1=193.1kWh 2=182.9kWh