pure (integration) urgent!

Let f(x) be a function with a continuous second derivative f''(x) and
I =∫(1 to 0) f(x) dx
(ai) show that I = f(1) - ∫(1 to 0) xf'(x) dx
(ii) show also that I = f(0) + ∫(1 to 0) (1-x)f'(x) dx
(iii) Using (i) and (ii), or otherwise, show that
I = [f(0) + f(1)]/2 - (1/2)∫(1 to 0) x(1-x)f''(x) dx
(b) Using (ai) and (ii), or otherwise, show that
│I - [f(0) + f(1)]/2│ ≦ K/4 where K is the greatest value of
│f'(x) │on [0,1]
(c) Using (aiii), or otherwise, show that │I - [f(0) + f(1)]/2│
≦ M/12 where M is the greatest value of │f''(x) │on [0,1]