边际收益是增加一个单位销售量 所引起的总收益变化。

Marginal revenue is the change in total revenue from an additional unit sold.

youdao

我认为，当价格下降时，单位销售量将会提升，但这些不会改变人们由购买cd转向网上下载的状况。

I think you'll see unit sales go up as prices go down, but this will not change the slide away from CDs towards downloading.

youdao

例如，可以明显地对销售量进行汇总，但单位价格应当是平均值。

For example sales amount can sensibly be summed but unit price should be averaged.

youdao