Let the domain of the function \( f(x) = \log_{2} \log_{4} \log_{6} (3 + 4x - x^2) \) be \( (a, b) \). If \( \int_{0}^{b-a} [x^2] \, dx = p - \sqrt{q} - \sqrt{r}, \, p, q, r \in \mathbb{Z}, \, \gcd(p,q,r) = 1 \), where \( [\cdot] \) is the greatest integer function, then \( p + q + r \) is equal to: