4. Suppose that the continuous random variables $(X, Y, Z)$ have a valid joint probability density function

$$f(x, y, z) = Kxyz^2, \quad 0 \le x, y \le 1, \quad 0 \le z \le 3.$$

Then, $E(Y) =$ (4) and $E(Y|X = \frac{1}{2}, Z = 1) =$ (5). Of course, you should find the value of $K$ first.