Finding the coefficient of Friction

[Simpleshot]

Homework Statement

A book has a mass of 400 g. When you slided the book against the floor with 5 N, it accelerated at the rate of -1.5 m/s2. What would the coefficient of friction between the book and the floor be?

Homework Equations

F = ma

W = mg

FN = - mg

The Attempt at a Solution

m=.400
fa: 5N
FN= 3.9 N
A: -1.5m/s

Can someone please explain how I should be finding the force of friction?

 

[PhanthomJay]

Your relevant equations should list the friction force formula (as a function of the coefficient of friction and the normal force).
Also, it's not F=ma, it's F_net = ma, so calculate the net force and from that you can get the friction force.