Interpret the following statements in terms of the relevant elasticity concept.
a. "As fuel for tractors has become more expensive, many farmers have shifted from plowing their fields to no-till farming. No-till acreage increased dramatically in the past 20 years."
b. "Fertilizer makers brace for a dismal year as fertilizer prices soar."
c. "When farmers are hurting, small towns feel the pain."
d. "The development of the Alberta oil sands may bring prosperity to many northern Alberta merchants."