What is the formula to calculate the price elasticity of supply?
a) (Change in quantity supplied) / (Average quantity supplied) ÷ (Change in price) / (Average price)
b) (Change in price) / (Average price) ÷ (Change in quantity supplied) / (Average quantity supplied)
c) (Change in quantity supplied) × (Average quantity supplied) ÷ (Change in price) × (Average price)
d) (Change in price) × (Average price) ÷ (Change in quantity supplied) × (Average quantity supplied)