Trigonometry · Challenge problem

On a running track, each lane runs around the two semicircular bends with a radius $1.2$ m larger than the lane inside it, and the lane $1$ runner's path on the bends has radius $36$ m. In a one-lap race (both straights and both bends), how many metres ahead of the lane $1$ runner must the lane $4$ runner start so that both run the same distance? Give the exact value.