A heavy-equipment salesperson can contact either one or two customers per day with probability 1/3 and 2/3 ,respectively .Each contact will result in either no sale or a 50,000$ sale ,with the probabilities 0.9 and 0.1 ,respectively .Give the probability distribution for daily sales .Find the mean and standard deviation of the daily sales .

I am completely confused with this Qn because I was unable to apply E(X) and V(X) here .

Can somebody explain me in detail ?

What is the meaning of E(X+Y) provided that X and Y are two random variables ?

What is the meaning of E(X-Y) ?

Thank You