When all producers' supplies are added together, the result is . The following graph shows the market supply of athletic shoes in Sportsburg, USA. Market Supply of Athletic Shoes in Sportsburg, USA $120 $100- Price per pair $80- $60 $40- $20 $0+ 0 1,000 2,000 3,000 4,000 5,000 Pairs per month At a price of $60 per pair, producers will want to sell pairs per month in Sportsburg, USA. At a price of they will want to sell 4,500 pairs per month. But at a price of $20 per pair, they will not want to sell any pairs. This occurs because a price of $20 a pair does not cover the producers' of producing the shoes. Although the price effect applies to nearly all products, it's weaker for some and stronger for others. To measure the strength of the price effect on supply, economists use a concept known as the price of supply. When producers can quickly and easily change the amount of resources they use after a price change, supply is usually (elastic, inelastic). In contrast, when it is costly and time consuming for producers to change the amount of resources they use, supply usually is (elastic, inelastic)