A downward sloping demand curve can be derived for a normal product by increasing its price in the consumer-behaviour model and noting

The statement seems to be incomplete, but I'll provide an explanation based on what you've given.

A downward sloping demand curve represents the inverse relationship between the price of a good and the quantity demanded, holding everything else constant. This is known as the law of demand. Here's how it can be derived in a consumer-behaviour model:

1. Assume we have a normal product, which is a good that consumers demand more of as their income increases.

2. Increase the price of this product. According to the law of demand, consumers will buy less of the product because it's now more expensive. This is because consumers have a limited budget, and when the price of one good rises, they will often substitute it for a cheaper alternative.

3. Plot the price of the product on the y-axis of a graph and the quantity demanded on the x-axis.

4. As you increase the price, note the corresponding decrease in quantity demanded.

5. Connect these points to form a curve. This curve will slope downwards from left to right, illustrating the inverse relationship between price and quantity demanded.

6. This downward sloping curve is the demand curve for the normal product.

Remember, this is a simplified explanation. In reality, many factors can affect demand, including changes in income, preferences, and the prices of other goods.