The initial profit-sharing ratio was \( 4:3:3 \), changing to a new equal sharing ratio of \( 1:1:1 \). For Arjun, the old share was \( \frac{3}{10} \) and the new share is \( \frac{1}{3} \). Arjun's sacrifice or gain is calculated as New Share - Old Share. Substituting the values, this becomes \( \frac{1}{3} - \frac{3}{10} \). The least common multiple of 10 and 3 is 30. Thus, \( \frac{1}{3} \) becomes \( \frac{10}{30} \) and \( \frac{3}{10} \) becomes \( \frac{9}{30} \). The sacrifice or gain is \( \frac{10}{30} - \frac{9}{30} = \frac{1}{30} \). As the result is positive, Arjun has a gain of \( \frac{1}{30} \). Therefore, the correct option is (B) Gain \( \frac{1}{30} \).