During the 1970s oil crisis in the United States, to what speed were maximum highway speeds set, according to the source?

1. The source ties this historical fact directly to fuel-efficient cruising speed and drag. 2. It states that during the 1970s oil crisis, maximum highway speeds were set at about 90 km/h, or 55 mi/h. 3. This speed limit sits close to the fuel-efficient cruising range described just before it in the same passage. 4. The other speeds offered are either far below or well above the figure the source names. _Source: OpenStax College Physics (CC BY 4.0), Ch 5 "Further Applications of Newton's Laws: Friction, Drag, and Elasticity", section 5.2 Drag Forces_