A demand curve is a graph relating the quantity sold and price, which shows the maximum number of units that will be sold at a given price. Three demand factors affect price:

(a) consumer tastes,

(b) price and availability of substitute products, and (c)

consumer income. These demand factors determine consumers’

willingness and ability to pay for products and services. Assuming these demand factors remain unchanged, if the price of a product is lowered or raised, then the quantity demanded for it will increase or decrease, respectively. The demand curve relates to a firm’s total revenue, which is the total money received from the sale of a product, or the price of one unit times the quantity of units sold.