Reaction Breakdown:
The given reaction involves the following steps:
Total Hydrogen Atoms in Reactants and Products:
Let's count the number of hydrogen atoms in the reactants (A) and products (B):
Total Number of Hydrogen Atoms: Adding the hydrogen atoms from both reactants and products gives:
Total number of hydrogen atoms in A and B is \( 5 \) (from \( \text{CH}_3\text{CH}_2\text{Br} \)) \( + 6 \) (from \( \text{CH}_3\text{CH}_2\text{OH} \)) = 10 hydrogen atoms.

Total number of hydrogen atoms in Product A and Product B is 10.
Complete the following reactions by writing the structure of the main products: 
Let R = {(1, 2), (2, 3), (3, 3)}} be a relation defined on the set \( \{1, 2, 3, 4\} \). Then the minimum number of elements needed to be added in \( R \) so that \( R \) becomes an equivalence relation, is: