Traffic signal: Traffic engineers study how long the yellow light for a traffic signal should be. For one intersection, the number of seconds n required for a yellow light is related to the average...

Traffic signal: Traffic engineers study how long the yellow light for a traffic signal should be. For one intersection, the number of seconds n required for a yellow light is related to the average approach speed v, in feet per second, by

If the approach speed is 80 feet per second (about 55 miles per hour), how long should the yellow light be?