3. Steam is distributed on a site via a high-pressure and low- pressure steam mains. The high-pressure mains is at 40 bar and 350°C. The low-pressure mains is at 4 bar. The high-pressure steam is generated in boilers. The overall efficiency of steam generation and distribution is 75%. The low-pressure steam is generated by expanding the high- pressure stream through steam turbines with an isentropic efficiency of 80%. The cost of fuel in the boilers is 3.5 $-GJ-1, and the cost of electricity is $0.05 KW-1.h-1. The boiler feedwater is available at 100°C with a heat capacity of K. Estimate the cost of the high-pressure and 4.2 kJ kg low-pressure steam.