Consider the Security Market Line (SML) under CAPM:

(a) Intuitively, what does it mean for a stock to have a of zero? What does it imply for his expected return under CAPM? Please provide a crisp but concise answer of roughly 3 sentences.

(b) Can a stock have a negative a? If no, why? Can you think of some example of assets that tend to have a negative betas? Please provide a crisp but concise answer of roughly 3 sentences.