(b) \((10\%)\) Show that \(\operatorname{E}(Y|\mathbf{x}) = x + \theta\). In accordance with the theory, the expected value of \(X + \theta\) is that of Y, namely, \(3\theta / 2\), and the variance of \(X + \theta\) is less than that of Y. Show the variance of \(X\) is in face \(5\theta^2 / 4\).