Answer
$µ_{2~days}\neµ_{7~days}\neµ_{28~days}$
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.
