Why is it not necessary to purchase product replacement warranties?

Uknow what i love about i ask a dumb question it is immediately answered but when i ask a real question it take like an hour to get answered

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?

On january 1, eastern college received $1,350,000 from its students for the spring semester that it recorded in unearned tuition and fees. the term spans four months beginning on january 2 and the college spreads the revenue evenly over the months of the term. assuming the college prepares adjustments monthly, what amount of tuition revenue should the college recognize on february 28?