A power plant, having a Carnot efficiency, produces $1.00 \mathrm{GW}$ of electrical power from turbines that take in steam at $500 \mathrm{K}$ and reject water at $300 \mathrm{K}$ into a flowing river. The water downstream is $6.00 \mathrm{K}$ warmer due to the output of the power plant. Determine the flow rate of the river.