A \(1 \mathrm{~m} \times 2 \mathrm{~m}\) sheet of plywood is attached to the roof of your vehicle after being purchased at the hardware store. At what speed (in kilometers per hour) in \(20^{\circ} \mathrm{C}\) air will the boundary layer first start becoming turbulent? At what speed is about 90 percent of the boundary layer turbulent?