6.
\begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{48f9a252-61a2-491d-94d0-8470aee96942-07_864_995_299_495}
\captionsetup{labelformat=empty}
\caption{Figure 1}
\end{figure}
The figure 1 shows sketch of the curve \(C\) with equation \(y = \mathrm { f } ( x )\).
$$f ( x ) = a x ( x - b ) ^ { 2 } , x \in R$$
where \(a\) and \(b\) are constants.
The curve passes through the origin and touches the \(x\)-axis at the point \(( 3,0 )\).
There is a minimum point at \(( 1 , - 4 )\) and a maximum point at \(( 3,0 )\).
a. Find the equation of \(C\).
b. Deduce the values of \(x\) for which
$$\mathrm { f } ^ { \prime } ( x ) > 0$$
Given that the line with equation \(y = k\), where \(k\) is a constant, intersects \(C\) at exactly one point,
c. State the possible values for \(k\).