Last week, smartphones cost $400. This week, the price of smartphones fell to $300. What will probably happen to the quantity of smartphones demanded?
does it go up or down?

Answer

Up

Explanation:

According to the law of supply and demand, the demand of a certain product will most likely increase if that product experience a decrease in price. (assuming that other factors remain the same.) this law become much more likely to occur among products that is not considered as basic necessities.

People tend to spend their income for tertiary products (such as smart phones) based on the levels of their disposable income. Products with lower price range tend to be most likely can be afforded by people with low disposable income.