Hi, I need help with part (b).

7. Suppose that f : [a, b] - R is a bounded Riemann integrable function. Define the area function for f by Af (20 ) = f(t) dt. a a Prove that for any xo E [a, b), Af is right continuous at Co. b) Give an example of a function f and a point to such that Af is not differentiable at xo. (You should explicitly calculate Af for your example so that I can see that it is not differentiable.)