Suppose that initially the petrol market is in equilibrium at a price of $2 per litre and a quantity of 45 million litres per month. Then a war in the Middle East disrupts production of oil, shifting the supply curve of petrol from S₁ to S₂. The price of petrol begins to rise and consumers protest.The government responds by setting a price ceiling of $2 per litre. Use the graph to answer the following questions.

Price (dollars per litre) $5.00 3.00 2.00 Demand 0 30 40 45 Quantity (millions of litres per month)