Max Force P on a 100kg Spool w/ \mu=0.3

[RedFURR]

The spool weighs 100kg, at piont A and B the $$\mu$$=0.3
Determine the maximum force P without causing the spool to move. (see attached)
This is what I attained from Back of the Book:

$$\Sigma$$F_x=0; 0=N_A-N_B(0.3)
$$\Sigma$$F_y=0; 0=N_A(0.3)+N_B+P-100(9.81)
$$\Sigma$$M_O=0; 0=P(0.6)+N_B(0.9)-0.3N_B(0.9)-0.3N_A(0.9)

Which is close to what I arrived at, but summing the moments I left out N_B(0.9) which I don't understand, isn't N_Bs arm of action 0?
Am I wrong? if so could you explain?
or, preferably, is the book wrong?

 

[LightHero]

Your results are correct. The book is wrong. The missing term in the summation of moments should be NB(0.9). This is because the moment arms for both N and B are 0.9 m, so the moment on each point must be taken into account when calculating the summation of moments.