Understanding Function Notation?

I have a question in my textbook that I can not figure out. I am still a little bit confused about all of this because I haven't done any of it in a while.

The question is:

Evaluate f(4) for each of the following:

a) f= {(1,5), (3,2), (4,1), (6,2)}

b) is a chart with x and f(x) values

c) is the equation f(x) 3x^2 - 2x + 1

d) is a graph

The only one I know how to evaluate is the equation. I am not sure what to do with the set of ordered pairs. once I can understand what needs to be done there, I am sure I'll understand how to do the other two. I am thinking that I need to take an ordered pair and make it into an equation but I am not sure? Hopefully someone can explain what this is asking? Thanks.