Barbara is a mortgage broker, who is paid by commission. When interest rates decline, she does a lot of business and earns a lot of money, as more people buy houses or refinance their mortgages. But when interest rates rise, business falls substantially. To diversify, Barbara should choose investments that a. provide a lower return than the market average. b. provide a higher return than the market average. c. pay lower returns when interest rates rise and higher returns when interest rates fall. d. pay higher returns when interest rates rise and lower returns when interest rates fall.

Google started as one of many internet search engines, amazon started as an online book seller, and ebay began as a site where people could sell used personal items in auctions. these firms have grown to be so large and dominant that they are facing antitrust scrutiny from competition regulators in the us and elsewhere. did these online giants grow by fairly beating competition, or did they use unfair advantages? are there any clouds on the horizon for these firms -- could they face diseconomies of scale or diseconomies of scope as they continue to grow? if so, what factors may limit their continued growth?