The boat moving south starts from D at 2PM and the boat heading east reaches D at 3PM. This implies that at 2PM, the boat moving east was 15 kms away from D.

Now suppose the boats are closest after t hours of the southward boat starts from D.

In this time, the south ward boat will be 20t kms away from D and

The east ward boat would be (15- 15t)kms away from D .

The position of boats A nd B would be as shown in the figure

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