Let X, Y, and Z be random variables, and let $Cov(\cdot,\cdot)$ denote the covariance operator as usual. Suppose that the variance of X is 0.7, $Cov(X,Y) = 0.4$, $Cov(X,Z) = 1.2$, and $Cov(Y,Z) = 0.8$. Find each of the following to two decimal places.

Part (a) $Cov( Y, X)$

Part (b) $Cov( X + , Z)$

Part (c) $Cov( Y , X + Z)$

Part (d) $Cov( X + Y, X + Z)$