The three words "TATA Assets Rock" are flashed such that the words individually are switched on at regular intervals of 4,7 and 9 seconds respectively and after they are switched on, the words are switched off after 2 sec, 4 sec and 5 sec respectively.
If at time '$t$' all the words happened to switch off simultaneously, find the least time '$t$' which all three words will switch on simultaneously.
Error(s) Found !!!