How can I figure out the non differentiable values of this function?

Question

Basically, I am trying to answer question B, but I am confused on what it's asking. I know that a function is differentiable at a point when there's a defined derivative at that point, but I'm confused on the non differentiable part. Could anyone help me explain and solve part B? Thanks.

Problem: https://i.stack.imgur.com/CkePs.png

Answer 1

A function is only differentiable where it is continuous. Looks like there are points on the curve that are not continuous. There are four separate functions shown here, each one that is continuous in their own right. But where they join can't be differentiated.