The Following MINITAB Output Display Presents the Results of a Hypothesis

The following MINITAB output display presents the results of a hypothesis test for the difference $\mu _ { 1 } - \mu _ { 2 }$ between two population means.
$\begin{array}{l}\text { Two-sample T for X1 vs X2 }\\\begin{array}{rrrrc} & \mathrm{N} & \text { Mean } & \text { StDev } & \text { SE Mean } \\\text { A } & 15 & 71.319 & 24.905 & 6.430 \\\text { B } & 15 & 50.450 & 24.951 & 6.442\end{array}\end{array}$

Difference $= \operatorname { mu } ( \mathrm { X } 1 ) - \mathrm { mu } ( \mathrm { X } 2 )$
Estimate for difference: $20.869$
$95 \%$ CI for difference: $( 3.028,38.710 )$
T-Test of difference $= 0 ($ vs not $= ) :$ T-Value $= 2.292686$
P-Value $= 0.029586 \quad$ DF $= 28$
How many degrees of freedom are there for the test statistic?

A) 27
B) 0.029586
C) 28
D) 20.869