Answer:
3.4%
Explanation:
Data provided in the question:
Normal rate of return = 6.5%
Expected Inflation rate  = 3.1 %
Now,
The  real​ risk-free rate of​ interest is given as
Real​ risk-free rate of​ interest = Normal rate of return  - Expected Inflation rate
Therefore,
Real​ risk-free rate of​ interest = 6.5% - 3.1%
or
Real​ risk-free rate of​ interest = 3.4%