secondOrderLossFunction

Second-order loss function in the second factorial moment form, as in Zipkin, Foundations of Inventory Management (2000):

G2(x) = (1/2) * Emax(X - x, 0) * max(X - x - 1, 0)

At x = 0 this evaluates to 0.5 * mu^2 (because for Poisson EX(X-1) = mu^2), NOT 0.5 * (mu^2 + mu).

Note: some references (notably parts of the operations-research and VBA/Python inventory literature) define second-order loss as 0.5 * Emax(X - x, 0)^2 instead. The two conventions differ by mu/2 at x = 0. KSL uses the factorial-moment form throughout.