A supply-demand graph can be described as having a demand curve that begins in the upper left and slopes downward to the lower right; and having a supply curve that begins in the lower left and slopes

a) When only supply decreases, the supply curve shifts to the left, causing the equilibrium price to increase and the equilibrium quantity to decrease. This happens because there is less product available for sale, making it harder for buyers to find what they need, resulting in higher prices. b) When only supply increases, the supply curve shifts to the right, causing the equilibrium price to decrease and the equilibrium quantity to increase. This happens because there is more product available for sale, making it easier for buyers to find what they need, resulting in lower prices. c) When only demand increases, the demand curve shifts to the right, causing the equilibrium price and quantity to increase. This happens because there is more demand for the product, making it more desirable and valuable, resulting in higher prices and more sales. d) When only demand decreases, the demand curve shifts to the left, causing the equilibrium price and quantity to decrease. This happens because there is less demand for the product, making it less desirable and valuable, resulting in lower prices and fewer sales.