The function

$f(x)=|4-x|+8x$

can be expanded as a piecewise$-$defined function, in the form

$f(x)=\{\begin{array}{ccc}4+7x& if& a0\\ C& if& b<mn>0</mn>\end{array}$

where each of the three expressions $a,b$ and $C$ may depend on $x.$

b$=?$

a $=?$

C $=?$