This is a comparison question. We first need to follow the argument. Machine Y produces more units per hour than machine X. Thus, the company is going to stop using X. The author says, not so fast, Machine X should still be used because it produces superior quality products than Y and uses the defective rate as support.
A) is wrong because we don't know how old Machine Y is, nor do we know how age factros into the quality the parts.
B) is correct because it shows that based on the defective rate - the support the author uses to indicate X is superior Y - Y and X are equivalent. If Y and X are equivalent in quality, then it makes sense to go with the Machine that produces more units per hour.
C) is wrong because we're talking about X and Y. A new machine is irrelevent to the author's argument or whether we should keep X.
D) This is a separate argument completely. Yeah, Machine Y might make more units than X and it might be less expensive and might have 100 other advantages. The author however focuses on QUALITY. That's the reason Machine X should be used. It is better quality than Machine Y. Therefore, the correct answer choice must relate to the quality of the units.
E) is wrong because it desn't counter the author's position. The author says that Machine X SHOULD be used. Detailing what a position or policy is does nothing to counter the author's normative argument.