b
(b)

\(\sum F y=0\)

\(\Rightarrow N - mg \cos \theta=0\)

\(\Rightarrow N = mg \cos \theta----(1)\)

\(Fx =0\) (as constant velocity \(\Rightarrow\) No acceleration)

\(\Rightarrow mg \sin \theta-\mu_{ k } N =0\)

\(\Rightarrow mg \sin \theta-\mu_{ k } mg \cos \theta=0\)

\(\Rightarrow \cos \theta\left(\tan \theta-\mu_{ k }\right)=0\)

\(\Rightarrow \mu_{ k }=\tan \theta=\tan 37^{\circ}=\frac{3}{4}=0.75\)