Problem 2. Using either the definition of integrable or Riemann's criterion involving upper and lower sums show that f : [0, 1] → R defined by f(x) = x for all x e [0, 1] is integrable, and find the...

Hello! I need your help with the question attached. If you can solve it, it will be great because it's quite important for me... Thank you !

Extracted text: Problem 2. Using either the definition of integrable or Riemann's criterion involving upper and lower sums show that f : [0, 1] → R defined by f(x) = x for all x e [0, 1] is integrable, and find the value x dx.