5.21 An engineer is trying to decide which process to use to reduce sludge volume pribr to disposal. Belt filter presses (BFP) will cost $203,000 to buy and $85,000 per year to operate. Belts will be replaced one time per year at a cost of $5500. Centrifuges (Cent) will cost $396,000 to buy and $119,000 per year to operate, but because the centrifuge will produce a thicker "cake", the sludge hauling cost to the monofill will be $37,000 per year less tharn for the belt presses. The useful lives are 5 and 10 5.2 years for alternatives BFP and Cent, respectively, and the salvage values are assumed to be 10% of the first cost of each process whenever they are closed down or replaced. Use PW evaluation to se- lect the more economical process at an interest rate of 6% per year over (a) the LCM of lives, and (b) a study period of 8 years. Are the decisions the same? 22 Tha nraduet dovelanment aroun of a hioh-tech