VTMO 2014 — Grade 6 — final Question 4

Vy travels at $5 \frac{\,\mathrm{km}}{h}$ on flat road, $4$ uphill, $6$ downhill. Outward travel takes $1 h = 36$ min, return $1 h = 39$ min. The flat part is $2.5$ km. Find total distance $VB$.