Answer
The results are ambiguous. We can conclude that $µ_{PpB}\neµ_{NB}$, but we could not conclude that $µ_{PpB}\neµ_{PB}$ or that $µ_{PB}\neµ_{NB}$.
There is at least one Type II error (when we do not reject $H_0$ when we should have rejected).
Work Step by Step
With the results from item (a) still available:
Select Stat -> ANOVA -> General Linear Model -> Comparisons
In Response select C3. In Type of comparison select Pairwise. In Method select Tukey. In Choose terms for comparisons select C2 (treatments).
Click OK.
