Ram, Shyam and Tarun started cycling from a point on a circular track $600 \mathrm{~m}$ long with speeds of $10 \mathrm{~m} / \mathrm{sec}$, $15 \mathrm{~m} / \mathrm{sec}$ and $20 \mathrm{~m} / \mathrm{sec}$ respectively. Find the time taken by them to meet at the starting point for the first time (in seconds).
(A) 120
(B) 60
(C) 240
(D) 600