Vivek was rowing a boat when he was 127.5km away from his destination, a leak developed in the boat due to the leak, 3.75 liters of water is entering the boat every 12.5 minutes, and there was an outlet system in the boat that threw out 4 liters of water in half hours. He also made a phone call to the rescue boat, which is coming to rescue him at speed of 6 km/h. If 75 liters of water is enough to sink that boat, then what should be the speed of Vivek's boat to save his boat from sinking till the arrival of the rescue boat?