From Mechanics

This question can be solved by examining the curve.

The lift has a speed of \displaystyle 1 \text{ m}{{\text{s}}^{\text{-1}}} halfway in the first part and halfway in the third part.

Inspection gives

\displaystyle \frac{3}{2}=1 \textrm{.}5 \text{ s}

and

\displaystyle 7+\frac{9-7}{2}=8 \text{ s}