Individuals filing income tax returns received an average refund of no less than $1056. consider the group of "last minute" filers who mail their tax returns during the last five days of the income tax period (typically april 10 to april 15). a researcher suggests that a reason individuals wait is that on average these individuals receive lower refunds than do early filers. for a sample of 400 individuals who filed a tax return between april 10 and 15, the sample mean refund was $910. based on prior experience, a population standard deviation may be assumed at 1600. from these sample results, and using a significance of 0.01, what conclusion could the researcher reach regarding the mean refunds of "last minute" filers?