Which of the following statements is true about the beta of a portfolio? If a portfolio's beta increases from 1.2 to 1.5, its required rate of return will increase by an amount equal to its market risk premium. If the beta of a portfolio doubles, its required return also doubles. Higher beta stocks have more company-specific risk, but do not necessarily have more market risk. If a stock has a negative beta, its required return is negative. If the beta of a stock is three, the stock's relevant risk is thrice as volatile as the market portfolio.