Carlos Long, a financial analyst, is having a meeting with Tony John, one of his private wealth clients. During the meeting John stated that he wanted to achieve an expected return of 15% from his portfolio. Long estimated that the market portfolio has an expected return of 25% and a standard deviation of 37%. The risk-free rate is 5.0%. If Long uses the capital allocation line as a benchmark, what standard deviation will John's portfolio have? Answer as a percentage to a single decimal place.
expected_return = 0.15
market_return = 0.25
market_std = 0.37
risk_free = 0.05
portfolio_std = (expected_return - risk_free) / (market_return - risk_free) * market_std
round(portfolio_std * 100, 1)