Why was it necessary for marshlall to take the trouble to explain why navigation should be considered as part of commerce

answer; i believe the correct answer is (117);

changes in factors like average income and preferences can cause an entire demand curve to shift right or left. this causes a higher or lower quantity to be demanded at a given price. demand curves relate the prices and quantities demanded assuming no other factors change. it is important for consumers to know this information, because it is crucial for them to know what they can afford and can't afford. i hope this .