X-axis: Quantity of ColdVax (units) Y-axis: Price ($) Curves: S (MPC): Supply curve representing the marginal private cost (MPC) of producing ColdVax. D (MPB): Demand curve representing the marginal private benefit (MPB) to consumers. MSB: Curve representing ColdVax's marginal social benefit (MSB), which includes both the direct benefit to vaccinated individuals and the positive externality to society. Equilibrium Points: QE: Equilibrium point where the supply curve (S) intersects the demand curve (D). This is where producers maximize profits and consumers maximize utility based on MPB, but it doesn't account for the positive externality. Q*: Socially optimal quantity of ColdVax, which lies on the MSB curve and maximizes total societal benefit, considering both private and external benefits