What are sum expectation and variance?

Take random variables $X$ and $Y$ with finite means and variances. How would you work out:

1. The expected value of $X + Y$
2. The variance of $X + Y$ In your answer, provide the general formulas, clarify the part covariance plays, and outline the special case in which $X$ and $Y$ are independent. Overview: The item tests comprehension of expectation, variance, and covariance, plus the ability to reason about the way sums of random variables influence their moments—specifically the role of covariance and the independent case—in the Statistics & Math domain.