Assume that your uncle holds just one stock, East Coast Bank (ECB), which he thinks has very little risk. You agree that the stock is relatively safe, but you want to demonstrate that his risk would be even lower if he held a portfolio. You obtain the following returns data for West Coast Bank (WCB). Measured by the standard deviation of returns, by how much would your uncle's risk have been reduced if he had held a portfolio consisting of 60% in ECB and the remainder in WCB? (Hint: Use the sample standard deviation formula.)

Year ECB WCB

2018 40.00% 40.00%

2019 -10.00% 15.00%

2020 35.00% -5.00%

2021 -5.00% -10.00%

2022 15.00% 35.00%

Average return = 15.00% 15.00%

Standard deviation = 22.64% 22.64%