For $f(x)=3x^4-8x^3+1$ find the following.

$($A$)f^{\text{'}}(x)$

$($B$)$ The slope of the graph of $f$ at $x=1$

$($C$)$ The equation of the tangent line at $x=1$

$($D$)$ The value$($s$)$ of x where the tangent line is horizontal

$($A$)f^{\text{'}}(x)=12x^3-24x^2$

$($B$)$ At $x=1,$ the slope of the graph of $f$ is $$