Difficulty is defined by (a) frequency of use, (b) frequency of spelling pattern, and (c) developmental norms. It is not difficult, then, for teachers to place students with words of appropriate difficulty based on simple measures of instructional level (Schlagal, 1996).
If one assumes that shifts in the supply curve of ethanol are solely due to the changing price of corn, then, up to an ethanol price of $2.90, the price of corn completely determines the price of ethanol. In other words, the price of corn drives the price of ethanol, not the other way around. This is actually quite logical since the amount of ethanol used is essentially fixed; consequently, something else must be driving the price of ethanol.
1 In 1860, German inventor Nikolaus Otto uses ethyl alcohol as a fuel in an early internal combustion engine. 2  In 1862 and 1864, a tax on alcohol was passed in the U.S. to pay for the Civil War, increasing the price of ethanol to over $2.00 per gallon. Ethanol production rises to the 4-billion-US-gallon (15,000,000 m 3) level. 2  Between 1997 and 2002, three million U.S. cars and light trucks are produced which could run on E85, a blend of 85% ethanol with 15% gasoline.