A farmer is deciding which crops to plant. Either three or four fields will be planted; in each field only one crop will be planted. Exactly the same fields that are planted the first year will be planted the second year, but no field will be planted to the same crop for two consecutive years. For each field, the farmer will choose from among five possible crops – corn, soybeans, alfalfa, rye, and barley – according to the following conditions: I. In any year, at least one field will be planted to a cereal grain; the possible grains include corn, rye, and barley only. II. The year after corn is planted in a field, either soybeans or alfalfa must be planted in that field.