Suppose that there are many stocks in the security market and that the characteristics of stocks A and B are given as follows:

stock A- expected return: 12% standard deviation= 4%

stock B- exected return: 19% standard deviation= 12%

correlation= -1

Suppose that it is possible to borrow at the risk-free rate, r_f. What must be the value of the risk-free rate? (Hint: Think about constructing a risk-free portfolio from stocks A and B.) (Do not round intermediate calculations. Round your answer to 3 decimal places.)

risk free rate= _____%