The correct answer is B) 305 N.
The maximum force of friction between the bookcase and the floor is given by
![F=\mu m g](/tpl/images/0003/6780/8ddfd.png)
where
![\mu=0.82](/tpl/images/0003/6780/2448f.png)
is the coefficient of friction
![m=38 kg](/tpl/images/0003/6780/0455a.png)
is the mass of the bookcase
![g=9.81 m/s^2](/tpl/images/0003/6780/26062.png)
is the gravitational acceleration.
By substituting the data of the problem into the formula, we find
![F=(0.82)(38 kg)(9.81 m/s^2)=305 N](/tpl/images/0003/6780/5cd4d.png)