▶ Demand Curve slopes Downward- It indicates more is purchased in response to fall in price. (i) Law of Diminishing Marginal Utility- This law states that as consumption of a commodity increases, Marginal Utility of each unit goes on diminishing. Accordingly for every every additional unit to be purchased, the consumer is willing to pay less and less of price. (ii) Income Effect- With fall in price of a commodity, the real income of the consumer increases. Accordingly demand for the commodity expands. ( iii) Substitution Effect- When own price of Commodity (X) falls it becomes cheaper in relation to commodity (Y). It is expansion of Demand (For X) due to Substitution Effect. (iv) Size of Consumer Group- When price of a commodity falls, many more buyers can afford to buy it. Accordingly demand for the commodity expands. (v) Different Uses- A good may have different uses. Milk, for an example, is used for making curd, butter, cheese, sweets, ice-cream etc. If price of milk...