Electric utilities pay less for low-quality coal per ton delivered than for high-quality coal. Yet more low-quality coal than high—quality coal must be burned to generate the same amount of electricity. Moreover, per ton of coal burned, low-quality coal generates more ash than does high-quality coal, and the disposal of ash is becoming more and more expensive.
The considerations above, if true, most strongly support which of the following claims?
A coal-burning utility might not be assured of benefiting economically by always adhering to the policy of keeping its overall coal purchasing costs as low as possible.
In those regions where the cost of disposing of coal ash is negligible, it is more expensive for coal-burning utilities to use high-quality coal than low-quality coal.
Transportation costs represent a smaller proportion of the cost per delivered ton for low-quality coal than for high-quality coal.
It is no less expensive to dispose of a ton of coal ash that results from the burning of high-quality coal than it is to dispose of a ton of coal ash that results from the burning of low-quality coal.
In regions where coal-ash disposal is the least expensive, reserves of low-quality coal are likely to decline at a faster rate than are reserves of high-quality coal.
单位体积的低质量煤所产生的灰比等体积的高质量的煤产生的灰尘更多,而且现在灰尘处理越来越贵。问must be true
choice a, 通过保证采购最低价格煤矿的策略,并不能保证这种方法在经济上最优的。correct
choice b, 在灰尘处理成本可以忽略不计的地方,使用优质煤比使用低质煤更加昂贵。incorrect, 无法得到生产相同的电量,低质量煤的价格和高质量煤的价格比较关系
choice d, 处理高质量煤产生的一吨灰的成本,并不比处理低质量煤产生的一吨灰的成本更便宜。incorrect,原本没有提及同等体积的灰尘处理成本关系
A: CORRECT. the information presented dose not clearly support a conclusion about whether it's economically beneficial for coal-burning utilities to minimize their coal-purchasing costs. Therefore, utilities relying solely on this information cannot be assured that it is. 我的理解:各类费用具体的临界值不知道,是无法得出确切的选择方案的,所以正确答案说的是might(可能)。
发相同电,低质量煤需要烧的比高质量煤多
低质量煤渣比高质量多,处理费在变得越来越贵
前面都是废话,最后越来越贵才是重点!!
一定要注意边读边总结!!
前提①:产生相同amount的electricity花费的低质量coal比高质量多。
前提②:低质量coal产生更多的ash,处理ash越来越贵==》more and more有点在暗示最红有一天处理ash的花费会超过购买低质量coal所带来的成本节约
一定要读懂每一个选项啊!!!不要盲目快进!!读完每一个选项之后仔细的去思考一下!!
pl
重新考察題目,發現幾個變量。分別為Cost of disposal(Cd),Qof ash(Qa),Quantity to burn(Qb),Energy generated(E)。有stimulus可知:
Qal>Qah if Qbl=Qbh; Cd(per ton) both Unknown; Qbl>Qbh if El=Eh. Btw Pl
感觉没什么方法啊,求教老师!!