A stock is expected to return 13% in an economic boom, 10% in a normal economy, and 3% in a recession. Which will lower overall expected rate of return of this stock?

a. an increase in the rate of return in a recession
b. an increase in the probability of an economic boom
c. a decrease in the probabnility of a recession
d. a decrease in the probability of an economic boom
e. an increase in the rate of return for a normal economy