a) Assuming the following returns and corresponding probabilities for asset A, if the expected return of Asset A is 15%, what is the standard deviation of Asset A?

Asset A
Rate of Return	Probability
10%	0.30
15%	0.40
20%	0.30

b) A firm has an operating cycle of 120 days, an average collection period of 40 days, and an average payment period of 30 days. Calculate the firm's average age of inventory in days. What does it indicate?