Meteorologist Paul Windward and geologist Rhaina Stone are rushing to a paleontology conference in Pecos Gulch. Paul lifts off
in his balloon at noon from Lost Wages, heading east for Pecos
Gulch Conference Center. With the wind blowing west to cast, he
averages a land speed of 30 km/h. This will allow him to arrive in
4 hours, just as the conference begins. Meanwhile, Rhaina is 160 km
north of Lost Wages. At the moment of Paul's liftoff, Rhaina hops
into an off-road vehicle and heads directly for the conference center.
At what average speed must she travel to arrive at the same time
Paul does?