9 The function f is defined for all real values of \(x\) as \(\mathrm { f } ( x ) = c + 8 x - x ^ { 2 }\), where \(c\) is a constant.
- Given that the range of f is \(\mathrm { f } ( x ) \leqslant 19\), find the value of \(c\).
- Given instead that \(\mathrm { ff } ( 2 ) = 8\), find the possible values of \(c\).