The correct option is(C): 10 km
\(X _{ COM }=\frac{ m _{1} x _{1}+ m _{2} x _{2}}{ m _{1}+ m _{2}}\)
\(R =\frac{\frac{ M }{4} x +\frac{3 M }{4} \times \frac{ R }{2}}{ M }\)
Horizontal range is given as
\(r_{\frac{M}{4}}=\frac{r}{2}+d=2+8=10km\)
\(=10 Km\)

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Method used for separation of mixture of products (B and C) obtained in the following reaction is: 
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