This problem presents us with a block of wood being dragged across a horizontal floor with an applied force of 32 newtons and we are told the velocity is constant. So if we start with our force diagram, we know we're going to have a force of gravity down and that's going to be our mass times 9.8 newtons per kilogram or 127.4 newtons. Because there's no other vertical forces, we know that our normal force is going to be equal in opposite and we know we've got a force of 32, so that's about quarter of that. Let's go about a quarter of the length. There's our applied force of 32 newtons and because it's at a constant velocity, we now can also identify that there must be a force backwards and there's none other listed, so that's got to be friction, which also equals 32 newtons. Problem asks us for what is the friction coefficient, which is the force of friction over the force normal, plug in our numbers 32, 127.4 newtons over newtons and that gives us 0.251 as our friction coefficient. No units necessary on that.