3. Hot water for a HX is supplied by a natural gas furnace. The hot water enters to HX at 90C at a rate of 20 kg/min. The system operates 24 H in a day and 365 days in a year. The system has an efficiency of 90 percent and cost of natural gas is $1.5 per therm (1 therm= 105500 kJ). The average temperature of cold water enters the HX at 15 C for a year. By assuming HX will recover 80 percent of the available heat in the hot water, determine heat transfer rate of HX and amount of money this HX will save the company per year from natural gas? Cphof 4180 J/KgC. (-