Answer:
810 stocks
Step-by-step explanation:
M and S can repurchase $480,000 / $25 = 19,200 stocks
the number of shares that you need to sell to offset the firm's leverage = total amount of stocks that you own x (total stocks repurchased / total stocks outstanding before buyback) = 2,700 x (19,200 / 64,000) = 2,700 x 0.3 = 810 stocks
Since your goal is to offset the firm's new leverage, you have to sell a proportional amount of your stocks compared to the whole repurchase transaction.