How Fast to Drive? Suppose Duke is driving to a nearby town to attend a dance party, and must decide how fast to drive. The marginal benefit of speed is the extra dance time he will get by driving faster, and the marginal cost is the additional risk of a collision. The marginal-benefit curve is negatively sloped, and the marginal-cost curve is positively sloped. Suppose Duke's favorite dance partner, Daisy, is grounded for makeup violations. In the absence of Daisy, Duke's from speeding