A special bumper was installed on selected vehicles in a large fleet. The dollar cost of body repairs was recorded for all vehicles that were involved in accidents over a 1-year period. Those with the special bumper are the test group and the other vehicles are the control group, shown below. Each "repair incident" is defined as an invoice (which might include more than one separate type of damage). Statistic _ Test Group Cmtr'ol Group Mean Damage X1 = $ 1,175 X2 = $ 1,731 Sample Std. Dev. 51 = $ 767 $2 = $ 813 Repair Incidents n1 = 17 n2 = 14 Source: Unpublished study by Thomas W. Lauer and Floyd G. Willoughby. (a) Construct a 98 percent confidence interval for the true difference ofthe means assuming equal variances. (Round your final answers to 3 decimal places. Negative values should be indicated by a minus sign.) The 98% confidence interval is from 4228.05: to 116.0583 (b) Repeat part (a), using the assumption of unequal variances with Welch's formula for df (Round the calculation for Welch's clf to the nearest integer. Round your final answers to 3 decimal places. Negative values should be indicated by a minus sign.) The 98% confidence interval is from |:| to |:|