Problem 508 | Friction

$N = 400 \sin 30^\circ + 200 \cos 30^\circ$

$N = 373.20 \, \text{ lb}$
 

$\Sigma F_x = 0$

$f + 200 \sin 30^\circ = 400 \cos 30^\circ$

$f = 246.41 \, \text{ lb}$
 

$f = \mu N$

$246.41 = \mu (373.20)$

$\mu = 0.66$           answer