The initial profit-sharing ratio is \( 4:3:3 \), and the new profit-sharing ratio is \( 1:1:1 \) (equal sharing).
For Arjun:
\[
\text{Old Share} = \frac{3}{10}, \quad \text{New Share} = \frac{1}{3}
\]
Calculate Arjun's sacrifice or gain:
\[
\text{Sacrifice or Gain} = \text{New Share} - \text{Old Share}
\]
Substitute values:
\[
\text{Sacrifice or Gain} = \frac{1}{3} - \frac{3}{10}
\]
Find the LCM of denominators \( 10 \) and \( 3 \), which is \( 30 \):
\[
\frac{1}{3} = \frac{10}{30}, \quad \frac{3}{10} = \frac{9}{30}
\]
\[
\text{Sacrifice or Gain} = \frac{10}{30} - \frac{9}{30} = \frac{1}{30}
\]
Since the result is positive, it represents a gain.
Hence, the correct answer is (B) Gain \( \frac{1}{30} \).