VTMO 2014 — Grade 7 — final Question 2

Vy travels $V$→$B$ on flat/uphill/downhill sections at $\frac{\frac{5}{4}}{6} \frac{\,\mathrm{km}}{h}$, taking $1 h = 36$ min; the return takes $1 h = 39$ min. The flat section is $2.5$ km. Find the route length.