electric field question

hi there i have just started an electricity course and was wondering
if any of you know where i could find an answer key for the text by
sears and zemansky called university physics. Or perhaps someone will
know how to to this question:
Positive electric charge is distributed along the y-axis with charged
per unit lenght of (lamda). Consider the case where charge is
distributed only between the points y=a and y=-a. For points on the
+x-axis, graph the x-component of the electric field as a function of
x for values of x between x=a/2 and x=4a.
My big question is how do you graph this?

 

I believe you should look at Gauss' Law...