Please solve : $4.$ Two blocks are connected by a string which goes over an ideal $($i$.$e$.,$ massless$)$ pulley as shown in the figure above. Block A has a mass of $3\mathrm{.}00$ kg and can slide along a rough plane inclined $\backslash (30\mathrm{.}0^\{\backslash$circ$\}\backslash )$ to the horizontal. The coefficients of static and kinetic friction between block $\backslash ($ A $\backslash )$ and the plane are $0\mathrm{.}400$ and $0\mathrm{.}250,$ respectively.

$($a$)$ What mass should block B have in order to start block $\backslash ($ A $\backslash )$ sliding up the ramp? $[$Answer: $2\mathrm{.}54$ kg $]$

$($b$)$ Now assume that the mass of block $\backslash ($ B $\backslash )$ is increased by $\backslash (50\backslash \%\backslash )$ from its value in $($a$).$ What is the kinetic energy of block $\backslash ($ A $\backslash )$ when block $\backslash ($ B $\backslash )$ has fallen $10$ cm $?$ Assume that the blocks started from rest.