Alvin, Calvin and Melvin are running laps around a track. Alvin runs a lap every \(4\) minutes, Calvin runs a lap every \(6\) minutes and Melvin runs a lap every \(9\) minutes. If they start off at the same point, how many minutes will it take before all three of them are back at the starting point?
Details and assumptions:
- A lap of the track refers to 1 complete round, back to the starting point.