Maximum and minimum prices — practice question

The diagram illustrates the market for eye tests. Which policy would allow the government to raise the quantity of eye tests from OQ1 to OQ2?

• Aa maximum price of OP3 per test
• Ba minimum price of OP2 per test
• Ca subsidy paid to opticians of P3–P2 per test
• Da subsidy paid to opticians of P3–P1 per test