hi please help me out

Derek loves nothing more than a delicious hot cup of tea. So much so that he drinks numerous cups of tea every single day. While Derek can convince himself that tea is healthy, he has noticed that he has been eating more cookies lately. Unfortunately, it is harder to argue that cookies are healthy. Derek has decided to keep track of how many cups of tea he drinks and how many cookies he eats each day. On any given day, letting X denote the number of cups of tea he drinks and Y denote the number of cookies he eats, Derek believes that the relationship between X and Y is described by the following joint probability distribution: 3; (Cookies) 4 5 7 2 0.2 0.2 0.1 :1: (Tea) 4 0.1 0.04 0.05 5 0.12 0.14 0.05 Calculate the variance of the number of cookies that Derek eats on any given day. Do not include any units in your