Mathematics Problem Help (Image Attached)?

[Jehan Nithyanandan]

This diagram shows part of the graph of y = f(x)

http://img220.imageshack.us/img220/4699/fofxir0.png

(a) Find f(3) - I found that to be 2.
(b) Solve f(x) = 6 - I read across the graph and found x = 2.
(c) Find ff(1) - How do you do this?
(d) Find an estimate for the gradient of the curve at the point where x = -1 - Again no idea on how to do this.

The equation f(x) = k, where k is a number, has 3 solutions between x = -2 and x = 4.

(e) Complete the inequalities which k must satisifiy.

...... < k < ........

The "...." denote a blank space where you need to fill in the answer. :P

Please could one of you Mathletes help me with the questions I can't do. Thanks!