The answer is: 720W The definition of Power is:P =L/t =→F⋅→s/t =→F⋅→s/t = →F⋅→v The ⋅ in the last formulation designate a scalar product, well-defined by: →v . →w = |v| |w| cos(ˆvw), the angle ˆvw is 0 because →F and →v are parallel, so the cosinus is 1. So: P=1800N⋅ 0,40m/s=720W.