Ans ittttaaa a

Dear stuent ,
As toppling exist if the C.O.M doesnot lie on the table . For the system to remain stationary and un-toppled, the moments due to weights must be balanced with that of normal reaction.
But, the normal reaction location is limited by the edge of the table.
(i) Stability of the Upper block and Sphere
Let the length of the upper block, beyond the lower block be y.
The normal force exerted by the lower block on the upper block is $3Mg/2$​
The farthest distance possible is when normal reaction acts at the edge.
Moment balance about the edge of the lower block gives$Mgy/2 = Mg(L/2-y)$
∴y=L/3
Now , Stability of Upper masses and lower block
For the farthest distance possible without toppling, normal reaction acts on the edge of the table.
Normal reaction exerted by the table is 
Mg+Mg+0.5Mg=2.5Mg
And , Fixing origin at the edge of the table,
Location of CG of lower block is x−y−0.5L
Location of CG of upper block is x−0.5L
Location of CG of sphere is x
Applying moment balance about the edge of the table, we have

$$\begin{gathered} Mg(x-y-0.5L)+Mg(x-0.5L)+0.5Mg\left(x\right)= 0 \\ \Rightarrow 5x =2(L+y) = 8L/3 \end{gathered}$$
∴x=8L/15
Regards

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