I can't seem to get it right. Please help.

does not indicate completion. Return to question Monthly rent paid by undergraduates and graduate students. Undergraduate Student Rents (n = 10) 800 810 830 680 690 820 760 610 1, 050 680 Graduate Student Rents (n = 12) 1, 150 900 910 870 770 890 750 810 940 920 900 810 Click here for the Excel Data File (a) Construct a 99 percent confidence interval for the difference of mean monthly rent paid by undergraduates and graduate students, using the assumption of unequal variances with Welch's formula for d.f. (Do not round the intermediate calculations. Round your final answers to 3 decimal places. Negative values should be indicated by a minus sign.) X Answer is complete but not entirely correct. The 99% confidence interval is from -237.320 X to 29 987