Let P(x), Q(x), and R(x) be three monic quadratic polynomials with only real roots, satisfying
\begin{aligned}
& P(Q(x))=(x-1)(x-3)(x-5)(x-7) \\
& Q(R(x))=(x-2)(x-4)(x-6)(x-8)
\end{aligned}
for all real numbers x. What is P(0)+Q(0)+R(0)?
Let P(x), Q(x), and R(x) be three monic quadratic polynomials with only real roots, satisfying
for all real numbers x. What is P(0)+Q(0)+R(0)?