how to you work this problem out to find the "Standard deviation of AB, E(R)a, E(R)b? can you show me step by step?

o What is the covariance of returns between stocks A and B? Year Return A 60% 20% Return B 35% 2017 2016 15% 2015 10% - 20% GAB = 433.3% or 0.0433 E(R2) = 30% E(RB) = 10%