Answer:
c= 1/26
Step-by-step explanation:
The joint probability mass function for X and Y must comply that:
[tex]\[\sum\]\sum\] c(x +y) = 1[/tex] for x∈{1,2,4} and y∈{1,3}
thus, all the possible values for the pairs (x,y) are:
(1,1) (1,3) (2,1) (2,3) (4,1) (4,3)
and then
c [(1+1)+(1+3)+(2+1)+(2+3)+(4+1)+(4+3)] = 1
c[26] = 1
c= 1/26