Try setting up a grid and filling in the probabilities:

To get the probabilities for the first column:

Pr(Y = 1, X = 1) = Pr(Y = 1 | X = 1) Pr(X = 1) = .

Pr(Y = 2, X = 1) = Pr(Y = 2 | X = 1) Pr(X = 1) = .

Pr(Y = 3, X = 1) = Pr(Y = 3 | X = 1) Pr(X = 1) = .

Pr(Y = 4, X = 1) = Pr(Y = 4 | X = 1) Pr(X = 1) = .

Make sure you understand where the red probabilities have come from .....

In a similar way you can fill in the other columns .....