Dear all,

If X is the amount of money (in dollars) that a salesperson spends on gasoline and Y is the corresponding amount of money for which he is reimbursed, the joint density of these two random variables is given by:

_________1/25((20-x)/x) for 10<x<20, x/2<Y<X

f(X,Y) = {

_________0, Elsewhere

Find

A| The marginal density of X

B| The conditional density of Y given X=15

C| The probability that the salesperson will be reimbursed at least $10 when spending $15

Can anybody help me on my way to solve the questions? I tried to look for some basic information regarding marginal/conditional/joint density functions, but I couldn't find some basic information that could help me solving this question.

Thank you very much in advance.