Which of the following statements is CORRECT?
a. Beta is measured by the slope of the security market line.
b. If the risk-free rate rises, then the market risk premium must also rise.
c. If a company's beta is halved, then its required return will also be halved.
d. If a company's beta doubles, then its required return will also double.
e. The slope of the security market line is equal to the market risk premium,