Problem: Expected value and variance of a difference

Problem

Suppose that $X_1$ and $X_2$ are independent random variable s where $E\left( X_1 \right)=μ_1, E\left( X_2 \right)=μ_2$ $Var\left( X_1 \right)=σ_1^2$ and $Var\left( X_2 \right)=σ_2^2$ .

• Find $E(X_1-X_2)$
• Find $Var(X_1-X_2)$ .