An Urn contains 7 red and 11 white balls. Draw one ball at random from the urn. Let X=1 if a red ball is drawn, and let X=-1 if a white ball is drawn. Give the pmf, mean, and Variance of X.
I know how to give the pmf, mean, and variance if X=0 or 1, but the -1 throws me off. How would i go about doing this? Thank you for any help!