Joint distribution struggles...

[SGS]

Ok so i am struggling when it comes to setting up the actual problem of joint distributions. Here is an example of what I mean. Suppose we roll two dice that have numbers 1,2,3,4 on their four sides. Let X be the maximum of the two numbers that appear and Y be the sum. Find the joint distribution of X and Y. How do you set up f(x,y)? Once I get this I can do the math, I am just unsure how to set these story problem type things set up. Thanks in advance.

SGS