The Following Display from a TI-84 Plus Calculator Presents A 95

Multiple Choice

The following display from a TI-84 Plus calculator presents a $95 \%$ confidence interval for the difference between two means. The sample sizes are $n _ { 1 } = 10$ and $n _ { 2 } = 15$ .

How many degrees of freedom did the calculator use?

A) -0.439
B) -41.874
C) 19.678187
D) 80.827