an investment firm offers three types of equity investments, a, b, and c. of the firm's clients, 30% invest in a, 50% invest in b, and 20% invest in c. the rates of return are 10%, 6%, and 7% for a, b, and c, respectively. what is the expected value of the total return rate for the firm's clients?
6.2%

7.1%

7.4%

8.2%