Aforce in the +x-direction with magnitude f(x)=18.0n−(0.530n/m)x is applied to a 8.40 kg box that is sitting on the horizontal, frictionless surface of a frozen lake. f(x) is the only horizontal force on the box. so, if the box is initially at rest at x=0, what is its speed after it has traveled 16.0 m? express your answer to three significant figures and include the appropriate units.