5. The joint discrete probability distribution of the random variables, $(X, Y)$, denoted $f_{X Y}$, is $$ f_{X Y}(x, y)=\frac{x+y}{30} \quad \begin{array}{cc} x=0,1,2,3 ; & y=0,1,2 W =0 & \text { otherwise } \end{array} $$ Find the marginal discrete distribution for $X, f_{X}$. SP.SS.386