The weekly demand for a certain drink, in thousands of liters, at a chain of convenience stores is a continuous random variable g(X) = X^2 + X - 2, where X has the density function
f(x) = { K(x - 1), if 1 < x < 2; 0, if otherwise }
(a) Find K.
(b) Find the expected value of the weekly demand for the drink.