Hypothesis Testing for Two Population Means Formula. Sigma is Given. Credit cards debt example

These are my lecture for University and College level students.
A credit card watchdog group claims that there is a difference in the mean
credit card debts of households in California and Illinois. The results of
a random survey of 250 households from each state are shown at the left.
The two samples are independent. Assume that sigma1 = $1045 for California
and sigma2 = $1350 for Illinois. Do the results support the group’s claim? Use
a = 0.05.