94.
The joint probability distribution of random variables X and Y is given by f (x, y)=k x y for x=1,2,3, y=1,2,3, and k is a positive constant. What is the probability that X+Y will exceed 5?
a.
1/9
b.
1/4
c.
1/36
d.
Cannot be determined
请教解题思路?
k要不要算出来,如何算呢?