If there are four clocks, one ticks after every 30 minutes, second one ticks aft

If there are four clocks, one ticks after every 30 minutes, second one ticks after every 45 minutes, third one ticks after every 1 hour and 45 minutes and fourth one ticks after every 15 minutes. They all ticked together at exactly 12 noon. Then when will they tick together next time ?

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