In order to estimate the difference between the average hourly wages of employees of two branches of a department store, the following data have been gathered.

Downtown store North Mall Store

Sample size 25 20

sample mean $9 $8

Sample standard deviation $2 $1

A 95% interval estimate for the difference between the two population means is?

I'm having trouble regarding this question I can't seem to figure out where to start at with the interval estimate