Identify When Each of the Following Companies Should Recognize Revenue

Identify when each of the following companies should recognize revenue.
a. Valero Energy - integrated petroleum company that sells crude oil, natural gas and petroleum and chemical products under short-term agreements at prevailing market prices
b. Boeing - airplane manufacturer whose revenue is derived largely from long-term fixed-price contracts with airlines
c. Wells Fargo - large commercial bank that earns interest on loans
d. Ford Motor Company - manufactures and retails automobiles, provides financing for dealers and customers