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$).$

$\backslash$table$[[$Statistic$,$Test Group,Control Group$],[$Mean Damage,${\stackrel{}{x}}_1=$$$1,101,{\stackrel{}{x}}_2=$$$1,766$

$($PLEASE ANWSER A and D$)$