Solve for a, b, and c plz!

Alibaba's stock has a 50% chance of producing a 25% return, a 30% chance of producing a 10% return, and a 20% chance of producing a 28% return. First Solve for Part a) What is their expected rate of return? b. What is their standard deviation of returns? c. What is their coefficient of variation? 7.0 21.0 9.9 7.03