A race track is in the form of a right triangle. The longer leg of the track is 2 km more than the shorter leg (both the legs being on a highway at right angle to each other). The start and end points are also connected to each other through a side road. The escort vehicle for the race took the side road and rode with a speed of 30 k/h and covered the two intervals along the highway during the same time with a speed of 42 k/h. Find the length of the race track.

1) 14 km
2) 10 km
3) 24 km
4) 36 km
5) 18 km