Dynamics - Using the coefficient of friction

[K.QMUL]

Homework Statement

You are to lower a safe of mass 260kg at constant speed downs skids 20.0m long, from a truck 2.0m high.
a) If the coefficient of friction between the safe and the skids is 0.25, do you need to pull the safe down or hold it back?

b)How great a force parallel to the skids is needed?

Homework Equations

F=μN

The Attempt at a Solution

Please see image

 

[arildno]

Looks correct.