In June 2008, the U.S. retail gas price jumped from $3 to $4 a gallon. This is a 33% increase in price from January 2008. During that time, the total quantity of gasoline purchased fell by 3%. Supplies of gasoline produced also decreased from 1 million barrels to 800,000 barrels. No viable substitute has been created to replace gasoline.
How do I calculate consumer and producer surplus from this info? I know its 1/2 x (price-optimal price) x quanitiy for consumer and 1/2 x price x quantity but I dont know which numbers I should put where. Also, how should I calc elasticity of demand, should I use the 33% price increase or should I use the price change from 3-4? Please give as much detail as possible.