(2) (Assignment 5) A solid E is defined by the inequalities $0 \le x \le 1$, $0 \le y \le 1$, and $0 \le z \le x^2 + y^2$. The temperature of the solid is given by the function $T(x, y, z) = 25 - 3z$. Find the average temperature of the solid using the formula \frac{1}{\text{volume of } E} \iiint_E T(x, y, z) dV.