At the end of this section the student should be able to:

• Define PED • Explain with examples the uses of PED • Compute PED given data and a formula • Interpret the meaning of the formula • Distinguish between elastic, inelastic and unitary elastic with reference to the formula • Distinguish between goods that obey the law of demand and goods that do not, with reference to the formula • Graphically illustrate and explain goods that have a perfectly elastic and perfectly inelastic PED • Outline the factors that influence PED • Define YED • Compute YED given data and a formula • Interpret the meaning of the formula • Distinguish between elastic, inelastic and unitary elastic with reference to the formula • Distinguish between normal goods and inferior goods, with reference to the formula • Define YED • Compute CED given data and a formula • Interpret the meaning of the formula • Distinguish between elastic, inelastic and unitary elastic with reference to the formula • Distinguish between complements and substitutes, with reference to the formula • Define PES • Compute PES given data and a formula • Interpret the meaning of the formula • Distinguish between elastic, inelastic and unitary elastic with reference to the formula • Outline the factors the influence PES