1.2: Binomial constants and term independent of $x$

The first 3 terms, in ascending powers of $x$, in the expansion of $(2 + bx)^{8}$ can be written as $a + 256x + cx^{2}$. Find the value of each of the constants $a$, $b$ and $c$.

Using the values found in part (i), find the term independent of $x$ in the expansion of $(2 + bx)^{8}\left(2x - \tfrac{3}{x}\right)^{2}$.