Question 4
Phuong Vy travels from her home $V$ to her grandmother's home $B$ along a route with level, uphill, and downhill sections. Her speeds are $5$ km/h on level ground, $4$ km/h uphill, and $6$ km/h downhill. The outward trip takes $1$ hour $36$ minutes, and the return takes $1$ hour $39$ minutes. If the level sections total $2.5$ km, how long is the route from $V$ to $B$?