$4.($A$)$ A $15\mathrm{.}0$ kg block is released from rest at point A in the figure below. The track is frictionless except for the portion between points $\backslash ($ B $\backslash )$ and $\backslash ($ C $\backslash ),$ which has a length of $6\mathrm{.}00$ m $.$ The block travels down the track, hits a spring of force constant $\backslash (2,150\backslash$mathrm$\{$~N$\}/\backslash$mathrm$\{$m$\}\backslash ),$ and compresses the spring $0\mathrm{.}250$ m from its equilibrium position before coming to rest momentarily. Determine the coefficient of kinetic friction between the block and the rough surface between points B and C $.$