Economics homework help!

Question No2)
A firm has decided to invest in a piece of land. Management has estimated that the land can be sold in 5 years for the following possible prices:
Price Probability
10,000 .20
15,000 .30
20,000 .40
25,000 .10
a. Determine the expected selling price for the land.
b. Determine the standard deviation of the possible sales prices.
c. Determine the coefficient of variation. What does it means?