An enviroillnental engineer is trying to decide between two operating pressures for a waste,vater irrigation system. If a high-pressure system is used, fe,ver sprinkle and less pipe ,vill be required, but the pu1nping cost ,vill be higher. The alternative is to use lo,ver pressure with 1nore sprinklers. The pu1nping cost is esti1nated to be $3 per 1000 cubic meters of ,vastewater pu1nped at the high pressure. Twenty-five sprinklers will be required at a cost of $30 per unit. In addition, 1000 1neters of alu1ninu1n pipe ,vill be required at a cost of $9 per 1neter. If the lower pressure system is used, the pu1nping cost will be $2 per 1000 cubic meters of ,vastewater. Also required ,vill be 85 sprinklers and 4000 1neters of pipe. The alu1ninum pipe is expected to last 10 years and the sprinklers 5 years. If the volu1ne of ,vastewater is expected to be 500,000 cubic meters per year, Use the present ,vo1ih 1nethod, which pressure should be selected if the company's mini1num attractive rate of return is 12% ?
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