# Discrete Probability Mass Function

1. Oct 18, 2011

### l46kok

1. The problem statement, all variables and given/known data
A gas supply company is trying to set up contracts with two clients, A and B. The company will make a profit of ten million dollars for each contract that is successfully agreed. The probability of agreeing a deal with client A is 1/4 and the probability of agreeing a deal with client B is 1/2. The decisions of the two clients are independent. Let X be the total profit that the company will make from the two clients.

a)Find the probability mass function of X

b)Find the mean and variance of X

3. The attempt at a solution

I'm having a problem with setting up the PMF for this question.

f_X(x) =
1/4 for X = A
1/2 for X = B

This makes absolutely no sense. Furthermore, the sum of PMF has to equal to 1 but in this case, it isn't. I'm completely lost, how do I set up the PMF for this?

Last edited: Oct 19, 2011
2. Oct 18, 2011

### LCKurtz

X is the total profit. You might start by listing the possible values X may take.

3. Oct 19, 2011

### l46kok

Twenty million dollars, ten million dollars and zero dollars??

(edit)nvm I figured out ty

Last edited: Oct 19, 2011
4. Oct 19, 2011

### LCKurtz

I guess that means "never mind" and "thank you". You're welcome. Sometimes it just takes a little hint.