Suppose that the market portfolio is equally likely to increase by 24% or decrease by 8%. Security "X" goes up on average by 29% when the market goes up and goes down by 11% when the market goes down. Security "Y" goes down on average by 16% when the market goes up and goes up by 16% when the market goes down. Security "Z" goes up on average by 4% when the market goes up and goes up by 4% when the market goes down. The risk-free rate is closest to: 0 0% O 16% O 8% 04%