Answer
$µ_{Lift−Off~Minus~1}=µ_{Return~Plus~1}\neµ_{Return~Plus~1~Month}$
Work Step by Step
With the results from item (b) 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 (treatmeants).
Click OK.
