If f(x) = 3a|4x - 4| - ax, where a is some constant not equal to zero, find f '(1)

The slope of an absolute function at the point where it evaluates to zero is undefined.
Here, when x=1, so |4x-4|=|4-4|=|0|, the slope is undefined.  This is where the vertex of the "V" on the graph of the absolute value function.

Did you get there answer to 44?