Can you tell the difference between a grain of rice from one farm from another grain from a different farm? Chances are you can't. And it's markets like this -with identical goods that leave producers to be price takers (rather than having some/much control of their price and quantity combination), and also where entry into and exit from the market are relatively easy, that the economy is supposed to work at its best. Examining how a producer in such a market structure maximizes its profit, why is this type of market structure deemed to be the most efficient and optimal?