The maximum flow rate of standard shower heads is about 3.5 gpm (13.3 L/min) and can be reduced to 2.75 gpm (10.5 L/min) by switching to low-flow shower heads that are equipped with flow controllers. Consider a family of four, with each person taking a 5 min shower every morning. City water at 15°C is heated to 55°C in an electric water heater and tempered to 42°C by cold water at the T-elbow of the shower before being routed to the shower heads. Assuming a constant specific heat of 4.18 kJ/kg • °C for water, determine
(a) Te ratio of the flow rates of the hot and cold water as they enter the T-elbow and
(b) The amount of electricity that will be saved per year, in kWh, by replacing the standard shower heads by the low-flow ones.