The answer is D Neither Goku nor Selina
a.

is a proper joint density function if, over its support,
is non-negative and the integral of
is 1. The first condition is easily met as long as
. To meet the second condition, we require

b. Find the marginal joint density of
and
by integrating the joint density with respect to
:


Then


c. This probability can be found by simply integrating the joint density:


The question is asking to calculate the zeros of the function f(x)=(5x^2+2x)/x, base on that and in my further calculation, the possible answer would be x=5. I hope you are satisfied with my answer and feel free to ask for more if you have questions and further clarifications