Let the probability mass function (p.m.f.) of a random variable \( X \) be \(P(X = x) = \binom{4}{x} \left( \frac{5}{9} \right)^x \left( \frac{4}{9} \right)^{4-x}\), for \(x = 0, 1, 2, 3, 4\), then \(E(X)\) is equal to