Determining size needed for settling tank given flow rate and detention time.

6.10) A final settling tank for a 2-million-gallon-per-day (2mgd) activated-sludge treatment plant it to be designed to have an average overflow rate of 800 g/day-ft^2. the tank needs to have a minimum detention time of 2.0 hr and to allow proper settling it must be at least 11 ft deep. If the tank is circular, what should its diameter and depth be?