(a) Expand \((2-3x)^4\), evaluating all of the coefficients.

(b) The sum of the first three terms in ascending powers of \(x\) in the expansion of

\((2-3x)^4\left(1+\frac ax\right)\)

is

\(\frac{32}{x}+b+cx,\)

where \(a\), \(b\) and \(c\) are integers. Find the values of \(a\), \(b\) and \(c\).