find $\displaystyle P_{f}= [-1,2], N_{f}= [-1, 2] $ and $\displaystyle T_{f}= [-1,2] $ if given that $\displaystyle f(x)= |x|+1 $ for $\displaystyle -1\leq x \leq 2 $

effort made;

given that $\displaystyle f(x)=|x|+1 $ for $\displaystyle -1\leq x \leq 2 $

we have

f(-1) = 2

f(2) = 3

so

$\displaystyle P_{f}[-1,2]= \sum_{j=1}^{2}[3-2]^{+} $

$\displaystyle = [1]^{+} $

please help prove-read if am on track, thanks