This was my answer for someone else question exactly like this :)
Mark you want me to tell him I can send you a photo of the photo you sent you send you
Answer:
D.
Step-by-step explanation:
Two events A and B are independent when

where
is the probability that event A occurs given that event B has occured.
A = randomly selected person is from California
B = randomly selected person preferred brand A
A|B = being a person from California and preferring brand A.
Hence,

Since
events are independent.
And we are given that
and want to find the value of x. Set f(x) to 16 and we get the equation:

Subtract both sides by 4

Divide both sides by 2

This is the answer. Let me know if you need any clarifications, thanks!