Suppose that x1, x2 and x3 are independent bernoulli random variables, each has expected value 2/3. • define x = x1 + x2 + x3. what is the expected value of x? what is the variance? • define y = 3x1. what is the expected value of y ? what is the variance? • is x a binomial random variable? • is y a binomial random variable? • calculate p(x = y ).