After analyzing sales data the owner of an electronics store

After analyzing sales data, the owner of an electronics store produced the following joint probability distribution of the number of iPhones (X) and Blackberries (Y) sold daily.

X Y 1 2 1 0.25 0.35 2 0.15 0.25

a. Find the marginal probability distribution of the number of iPhones sold daily.

b. Compute the expected number and variance of iPhones sold daily.

Solution