"When you both stop, I stop" - Centre Of Mass

Two particles $A$ and $B$ are situated on a horizontal table top of infinite surface area whose surface is considered as the $x-y$ plane. The mass of $A$ is $1~kg$ and that of $B$ is $2~kg$ . At time $t=0$ , particle $A$ is at $(3,0)$ and particle $B$ is at $(0,9)$ . Both particles are given initial velocites:

• $3~ms^{-1}$ to $A$ along positive $x$ -axis and

• $6~ms^{-1}$ to $B$ along positive $y$ -axis.

If the coefficient of friction between each particle and the table top is $\mu = 0.2$ & the coordinates of the position of the centre of mass of $A$ and $B$ , where it comes to rest can be expressed as $\left(\dfrac{a}{b},\dfrac{c}{d}\right)$ , where $\left\{a,b\right\}$ and $\left\{c,d\right\}$ are pairwise co-prime positive integers, then enter your answer as

$\displaystyle (c+d)-(a+b)$ .

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