Given Reactions:
Correct Answer: The correct answer is 3.
\[ \text{CH}_3\text{COONa} \longrightarrow \cdot \text{CH}_3 \]
\[ \text{C}_2\text{H}_5\text{COONa} \longrightarrow \cdot \text{C}_2\text{H}_5 \]
\[ 2 \cdot \text{C}_2\text{H}_5 \longrightarrow \text{CH}_3 - \text{CH}_2 - \text{CH}_2 - \text{CH}_3 \]
\[ 2 \cdot \text{CH}_3 \longrightarrow \text{CH}_3 - \text{CH}_3 \]
\[ \cdot \text{CH}_3 + \cdot \text{C}_2\text{H}_5 \longrightarrow \text{CH}_3 - \text{CH}_2 - \text{CH}_3 \]
Consider the following reaction sequence.

In the given figure, the blocks $A$, $B$ and $C$ weigh $4\,\text{kg}$, $6\,\text{kg}$ and $8\,\text{kg}$ respectively. The coefficient of sliding friction between any two surfaces is $0.5$. The force $\vec{F}$ required to slide the block $C$ with constant speed is ___ N.
(Given: $g = 10\,\text{m s}^{-2}$) 
Method used for separation of mixture of products (B and C) obtained in the following reaction is: 