A box of mass m = 18.0 kg is initially at rest at the bottom of a rough plane that is inclined at an angle of θ = 20.0° above the horizontal. You push horizontally on the box with a constant force Fa that has a magnitude of 115 N. After you have pushed the box 1.50 m up the incline, it is traveling with a speed of 0.800 m/s. What is the coefficient of kinetic friction between the box and the plane?