Answer: 0.4%
Step-by-step explanation:
Given that,
At every time a fund manager trades stock, then
Transaction costs = 0.4% of the value of the trade
Portfolio turnover rate = 50% ; On an average, 50% of the portfolio stock is sold and exchange with the other securities every year.
Trading costs on selling orders = 0.4%
Trading costs on buying orders = 0.4%
Therefore,
Total return of the portfolio reduced by trading costs:

= 0.4%