The beta of the portfolio must be 1.50.
Beta is a measure of the systemic risk of a portfolio. The value of beta can be determined using the capital asset pricing model.
According to CAPM :
Expected portfolio return = risk free + beta( expected market return - risk free return)
18% = 6% + b(14 - 6)
18% = 6% + 8b
18% - 6% = 8b
12% = 8b
b = 12 / 8 = 1.50
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