Answer:
the beta of stock₂ = 1.69
Explanation:
the weight of each security is ¹/₃ of the portfolio:
the portfolio's beta is 1
1 = (¹/₃ x 0) + (¹/₃ x 1.31) + (¹/₃ x ?)
1 = 0.437 + (¹/₃ x ?)
1 - 0.437 = (¹/₃ x ?)
0.563 = (¹/₃ x ?)
? = 0.563 / ¹/₃ = 1.689 = 1.69
the beta of stock₂ = 1.69