Myers Business Systems is evaluating the introduction of a new product. The possible levels of unit sales and the probabilities of their occurrence are given next:

Possible Market Reaction	Sales in Units			Probabilities
Low response		20			.30
Moderate response		35			.20
High response		45			.20
Very high response		60			.30

b. What is the standard deviation of unit sales? (Do not round intermediate calculations. Round your answer to 2 decimal places.)