The functions f and g are defined for \(x \in \mathbb{R}\) by

\(f : x \mapsto 3x + a,\)

\(g : x \mapsto b - 2x,\)

where \(a\) and \(b\) are constants. Given that \(ff(2) = 10\) and \(g^{-1}(2) = 3\), find

1. the values of \(a\) and \(b\),
2. an expression for \(fg(x)\).