Draw two figures: (a) one showing that if the demand curve did not shift but the supply curve did, we could derive the demand curve for the commodity by simply connecting the observed price-quantity data points and (b) the other showing that if the supply curve did not shift but the demand curve did, we could derive the supply curve of the commodity by simply connecting the observed price-quantity data points. (c) In which sector of the economy is each of these cases most likely to occur? Why?