Confidence interval for difference in mean sales of burgers

Can someone please help with this question?

The owner of two fast food outlets wishes to compare the sales per day at the two locations. The mean number of Mushroom Burgers sold per day for 40 randomly selected days at the North Side location was 29 with a sample standard deviation of 3.5. An independent random sample of 35 days at the South Side location showed mean sales of 34 Mushroom Burgers per day with a standard deviation of 2.9. Compute a 98% confidence interval for the difference in the mean sales of Mushroom Burgers at the two locations.

Assuming normal distribution.

\(\displaystyle \L\\(\overline{x}_{1}-\overline{x}_{2})-z\sqrt{\frac{{\sigma}^{2}_{1}}{n_{1}}+\frac{{\sigma}^{2}_{2}}{n_{2}}}<{\mu}_{1}-{\mu}_{2}<(\overline{x}_{1}-\overline{x}_{2})+z\sqrt{\frac{{\sigma}^{2}_{1}}{n_{1}}+\frac{{\sigma}^{2}_{1}}{n_{2}}}\)

thanks,

but does it make sense that the answers are negative?

sarahtee said:

does it make sense that the answers are negative?

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It might help if you showed all your work and reasoning, so the tutors know what you mean.

Thank you.

Eliz.